NOVELTY - Preparing roxburgh rose proanthocyanidin comprises (i) extracting roxburgh rose juice using roxburgh rose fruit, crushing by using a crusher, and pressing roxburgh rose pulp, collecting fruit juice squeezing liquid for the first time, uniformly adding water, extracting for the second time, (ii) uniformly mixing the second fruit juice squeezing slag and ethanol, (iii) passing the combined roxburgh rose proanthocyanidin extract liquid through an ultra-filter, (iv) preparing roxburgh rose anthocyanin purified solution, and (v) preparing roxburgh rose anthocyanin powder.    USE - The method is useful for preparing roxburgh rose proanthocyanidin.    ADVANTAGE - The method: is economical, carried out under mild reaction conditions, safe, reliable and environmental friendly; saves energy; makes use of device which is simple; does not discharge waste; and produces product with high purity, good solubility and strong oxidation resistance. The product is utilized in the field of cosmetics, health products and medicine industries.    DETAILED DESCRIPTION - Preparing roxburgh rose proanthocyanidin comprises (i) extracting roxburgh rose juice using roxburgh rose fruit comprises crushing the fruit by using a crusher, and pressing, mixing the crushed roxburgh rose pulp and pure water, where the ratio of mass of pulp (g):volume of 15-25 degrees C pure water (in ml) is 1:10-30, pumping the mixture into an extracting tank, stirring and extracting for 15-30 minutes for the first time, collecting fruit juice squeezing liquid for the first time, introducing to a storage tank, screw pressing the remaining first fruit juice squeezing slag, uniformly adding purified water, where the ratio of mass of first press fruit juice squeezing slag (in g):volume of 15-25 degrees C pure water (in ml) is 1:5-20, then extracting for 15-30 minutes for the second time, collecting the second fruit juice squeezing slag and the second fruit juice, introducing the second fruit juice after squeezing the liquid in the storage tank containing first fruit juice, where the vacuum degree of the tank is 0.1 MPa, temperature is 50 degrees C and vacuum concentrating to 25-40%, (ii) uniformly mixing the second fruit juice squeezing slag and ethanol solution, where the ratio of mass of second fruit juice squeezing slag (g):volume (in ml) of 15-45 degrees C ethanol (40-60%) is 1:10-30, pumping into the extracting tank, extracting for 30-60 minutes under the condition of stirring, respectively collecting the first roxburgh rose proanthocyanidin extract residue and the first roxburgh rose proanthocyanidin extract liquid, introducing the collected first roxburgh rose proanthocyanidin extract liquid into the storage tank, where the ratio of mass of first roxburgh rose proanthocyanidin extract residue (in g) and volume (in ml) of 15-45 degrees C ethanol (40-60%) is 1:5-20, pumping the mixture into the extracting tank, extracting for 30-60 minutes under the condition of stirring, respectively collecting the second of roxburgh rose proanthocyanidin extract residue and the second of rose anthocyanin extracting solution, introducing roxburgh rose proanthocyanidin extract liquid for the second time into the chamber, and combining roxburgh rose proanthocyanidin extract liquid for the first time, (iii) passing the combined roxburgh rose proanthocyanidin extract liquid with a molecular wt. cut off 5000-10000 Da, through an ultra-filter under the pressure of 0.1-0.2 Mp, carrying out first ultra-filtration, collecting the first filtrate and first ultrafiltration retentate, where the retentate volume is reduced to 1/10 of its original volume, pumping the collected first ultra-filtration filtrate into the storage tank, adding the purified water to the first ultrafiltration retentate, supplementing to the original volume under same conditions until the retentate volume is reduced to 1/10 of the original volume, collecting the second ultrafiltration filtrate and second ultrafiltration retentate, mixing the first ultrafiltration filtrate into the second ultrafiltration filtrate, pumping the second ultrafiltration retentate into the spray dryer, and spray drying at 135-160 degrees C, (iv) preparing roxburgh rose anthocyanin purified solution comprises introducing the mixed filtrate into an adsorption resin column (Amberlite XAD7HP (RTM: Adsorber resin) or ADS-17 (RTM: Macroporous absorption resin) or DM130), where the flow rate is 2-6 times/hour, collecting the roxburgh rose anthocyanin effluent, loading the effluent into the adsorption resin column, washing the resin column with 1-3 times by volume of water, collecting the solution, washing the effluent load on the adsorption resin column, eluting by using 50-70% of ethanol with a flow rate of 2-6 times/hour, detecting the absorbance of eluent UV spectrophotometer at 280 nm, when the eluent reaches absorbance of 280 nm, collecting the eluent and unloading the rose anthocyanin macroporous absorption resin, and (v) preparing roxburgh rose anthocyanin powder by pumping the collected eluent are into a reverse osmosis counter, where the operation pressure is 1.5-2.5 Mpa and the mass concentration of roxburgh rose proanthocyanidins is 8-15%, respectively collecting the reverse osmosis permeate liquid and concentrated liquid for collecting reverse osmosis concentrated solution, concentrating in a vacuum compressor, where the vacuum degree is 0. 06-0.09 MPa and temperature is 50-60 degrees C, carrying out vacuum concentration to the concentrated solution until there is no ethanol smell, respectively collecting the condensed solution and concentrated solution, pumping the concentrated solution into a spray dryer, where the air inlet temperature is 130-150 degrees C, the air outlet temperature is 80-95 degrees C, the spraying speed is 8000-12000 revolutions/minute, spray-drying, collecting the dried powder to obtain product with average molecular weight of 846 Da and purity of 90-95%.