The invention discloses a preparation method of 3,3,3-trifluoropropene carbonate, belonging to the technical field of cosolvents or additives for battery electrolytes. 3,3,3-trifluoropropene carbonateis prepared from 3,3,3-trifluoro-1,2-epoxypropane. The method comprises the following steps: A, mixing 3,3,3-trifluoro-1,2-epoxypropane with an aqueous hydrochloric acid solution having a concentration of 0.1 mol/L, adding perfluorosulfonic acid resin, carrying out a reaction at 35-45 DEG C for 3-5 h, conducting natural cooling to room temperature, then adding an alkaline solution with a pH valueof 7.0, carrying out a reaction for 30-60 min, and carrying out reduced-pressure distillation, and performing filtration and fractionation to obtain 3,3,3-trifluoro-1,2-propanediol; and B, with methylbenzene as a solvent, adding dimethyl carbonate and the 3,3,3-trifluoro-1,2-propanediol obtained in the step A, adding a palladium-copper catalyst, carrying out heating to 50-120 DEG C, carrying outreacting for 4-5 hours, and distilling off methanol to obtain the 3,3,3-trifluoropropene carbonate. According to the method, the 3,3,3-trifluoro-1,2-epoxypropane is adopted as the raw material to prepare the 3,3,3-trifluoro-1,2-propanediol, and the 3,3,3-trifluoro-1,2-propanediol and dimethyl carbonate are subjected to catalytic synthesis under the action of the palladium-copper catalyst, so operability is high, and the yield of the final product 3,3,3-trifluoropropene carbonate reaches 87% or above.