The invention provides a preparation method of TGEV (transmissible gastroenteritis virus). According to the method, in a bioreactor, an ST cell is adopted as the host cell, microcarrier culture is employed for proliferation of TGEV, and at the same time efficient condition parameters are designed. The culture efficiency is significantly improved, the cell density is enhanced by 3-5 times than spinner bottles, the virus titer is high, and is increased from the 10<7.0-7.3>TCID50/ml of spinner bottle technique to 10<7.7>-10<8.5>TCID50/ml, and the titer is enhanced by 5-10 times. At the same time, a high titer antigen needs a high dilution factor during use, so that the content of heterologous protein in a unit volume antigen is reduced indirectly, thereby lowering the side reaction incidence of vaccines prepared with heterologous protein as the antigen. The technology is low in cost, and compared with the practice of selecting a traditional basic medium, the harvest time is greatly shortened, the interassay difference is small, and the process is stable.