Preparation method of long-acting ceftiofur free acid crystal

The invention provides a method for preparing long-acting ceftiofur free acid. The method is different from past preparation methods. The aim achieving method includes the steps that ceftiofur free acid serves as a raw material, ceftiofur free acid is dissolved in an organic solvent miscible with water, a transparent ceftiofur free acid solution is prepared, a catalytic amount of crystal modifier and surfactant are added into the solution, after the materials are completely stirred, the solution is added into water, solids are obtained after crystallization is completed, after aging is completed, filtering and drying are carried out, and the ceftiofur free acid product is prepared. The ceftiofur free acid crystal product prepared through the method has an excellent slow release effect. The experiment shows that the ceftiofur free acid crystal product prepared through the method is slowly released inside and outside animal bodies, the release speed is constant, no fluctuation is generated, and high bioavailability is achieved.