NOVELTY - A natural octopus carnitine is prepared by cleaning cephalopod by removing contaminants, crushing raw material, placing material in reaction kettle, adding 3-6 times amount of water, controlling reaction at 50-100 degrees C, stirring for 1-4 hours to obtain carnitine octopus extract, subjecting extract to continuous flow centrifugation at 3000-13000 rpm and removing solid impurities in extract to obtain extracting solution, and performing centrifugation extraction solution through membrane to remove impurities in which membrane pore size is 0.05-0.8 mu m with molecular weight of 10000-200000 Da.    USE - Preparation of natural octopus carnitine (claimed).    ADVANTAGE - Preparation process is easy, environment-friendly, and efficient and has high product purity and selectivity, mild temperature operation, no phase change and chemical change, and low energy consumption.    DETAILED DESCRIPTION - A natural octopus carnitine is prepared by cleaning cephalopod by removing contaminants, crushing raw material, placing material in reaction kettle, adding 3-6 times amount of water, controlling reaction at 50-100 degrees C, stirring for 1-4 hours to obtain carnitine octopus extract, subjecting extract to continuous flow centrifugation at 3000-13000 rpm and removing solid impurities in extract to obtain extracting solution, performing centrifugation extraction solution through membrane to remove impurities in which membrane pore size is 0.05-0.8 mu m with molecular weight of 10000-200000 Da, operating pressure is 0.1-0.5 MPa, and concentration factor is 5-10 times, adding 0.2-1 times amount of water, subjecting liquid to secondary membrane separation to decolorize and remove impurities from liquid in which secondary membrane is cutoff roll-nanofiltration membrane with molecular weight of 200-2000 Da, operating pressure is 0.5-1.5 MPa, and concentration factor is 6-15 times, adding 0.2-1 times water, subjecting liquid to 3 pairs of secondary membrane for concentration in which sodium chloride rejection of 3 pairs of secondary membrane is greater than or equal to 99% of rolled reverse osmosis membrane component, operating pressure is 1-2 MPa, and concentration factor is 10-20 times, subjecting liquid to strong acid cation exchange column in which strong acid cation exchange column resin volume is 1 BV, reverse osmosis concentration amount of column is 1-2 BV, sample flow rate is 0.5-2 BV.hour-, concentration of ammonia in eluent is 1-2 mol.L-, amount of eluting agent is 2-3 BV, and eluting flow rate is 1-2 BV.h-, subjecting to basic anion exchange column in which basic anion exchange column resin volume is 1 BV, column volume is 1-2 BV, sample flow rate is 0.5-2 BV.hour-, concentration of ammonia in eluent is 1-2 mol.L-, amount of eluent is 2-3 BV, and eluting flow rate is 1-2 BV.h-, subjecting to medium-pressure chromatography in which chromatographic filler is 8-18 carbon-containing mobile phase of aqueous acetic acid with concentration of 0.01-0.3%, concentrating under reduced pressure, and drying to obtain product with 95% purity.