NOVELTY - Alcohol-based fuel composite auxiliary agent comprises (in vol.%) co-solvent (60-70), power improving agent (10-20), solubilizer (5-10), antioxidant corrosion inhibitor (1-5), anti-swelling agent (1-3) and brightening agent (1-2). The agent product is prepared under stirring condition at 50-70 revolutions/minute and refluxing at 40 degrees C for 20 minutes.    USE - The auxiliary agent is useful for engines.    ADVANTAGE - The auxiliary agent: is not layered when encountering water; has good phase stability, does not have emulsification, wide buffer index and keeps material clear and transparent after adding the brightening agent; and is provided with oil quality close to the commercial #93 and #97 vehicle with unleaded petrol which can be started at high temperature and also in winter, is simple in preparation, and environmental friendly.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing alcohol-based fuel composite auxiliary agent, comprising (i) preparing co-solvent by introducing 3-14% of normal butanol, 6-27% of tertiary butanol, 15-35% of isopropanol, 3-14% of n-amyl alcohol, 3-14% of isoamylol and 3-14% of n-caprylic alcohol to a reaction kettle in batches, stirring them at 100-120 revolutions/minute when the temperature is at 50 degrees C, refluxing the mixture for 30 minutes in a closed environment, allowing to stand the mixture and cooling it until the mixture is clear and transparent, and storing, (ii) preparing solubilizer by adding cyclohexanol and ethylene glycol monobutyl ether to a refluxing glass stirring kettle based on the volume ratio of (40-60):(40-60), stirring the mixture at 50-60 revolutions/minute at 40 degrees C, refluxing the mixture for 20 minutes, cooling the mixture to room temperature, adding hexamethylphosphoric triamide which is 15-35% of the total volume and continuously increasing the temperature to 50 degrees C, stirring the mixture for 20-30 minutes, and cooling, (iii) preparing power improving agent by introducing 20-40% of kerosene, 20-40% of dimethylbenzene, 10-30% of dimethyl carbonate and 10-30% of N,N-dimethylaniline in a refluxing and closed glass reaction kettle, stirring at 50-70 revolutions/minute at 40 degrees C, performing reaction for 30-60 minutes, allowing to stand and cooling, and storing, (iv) preparing antioxidant corrosion inhibitor by adding 56-77% of zinc dialkyl dithio phosphate and 23-44% of N,N'-di-sec-butyl-1,4-phenylenediamine to the refluxing and closed glass reaction kettle, stirring them at 50-70 revolutions/minute, gradually increasing the temperature to 35-40 degrees C, performing reaction for 20-30 minutes until the mixture is transparent and dark red, allowing to stand and cooling, and storing, (v) preparing anti-swelling agent by adding 65-80% of co-solvent and 15-35% of petroleum calcium sulfonate to the glass reaction kettle, increasing the temperature and uniformly stirring the mixture, where the stirring speed is at 50-70 revolutions/minute, and the temperature is controlled at 40 degrees C, terminating heating and stirring when the material is changed to clear and transparent liquid, cooling and allowing to stand the liquid, and storing, (vi) preparing brightening agent by adding (in vol.%) methyl ricinoleate (20-45), methyl ester of Cornus wilsoniana oil (20-45) and tung oil methyl ester (20-45) to the reaction kettle, performing reaction for 30-40 minutes at 90-120 degrees C until the mixture is clear and transparent, and cooling and allowing to stand the liquid, and (vii) preparing auxiliary agent by adding (in vol.%) co-solvent (60-70), power improving agent (10-20), solubilizer (5-10), antioxidant corrosion inhibitor (1-5) and brightening agent (1-2), stirring at 50-70 revolutions/minute at 40 degrees C, stirring and refluxing the mixture for 20 minutes until the mixture turns to red color, clear and transparent to obtain the product.