The invention discloses a serratia marcescens vaccine.The active ingredient of the serratia marcescens vaccine is a biological pure culture of serratia marcescens.The serratia marcescens is preserved in China General Microbiological Culture Collection Center on January 11, 2016 with the preservation number of CGMCC NO.11987.The invention further discloses a preparation method of the serratia marcescens vaccine.The serratia marcescens vaccine is prepared from the biological pure culture of the serratia marcescens through a proper separation method.According to the proper separation method, centrifugation is carried out at 4,000-6,000 rpm for 30-60 min, supernatant is discarded, sediment is inactivated, centrifugation is carried out again, supernatant is discarded, sediment is washed and centrifuged, and the serratia marcescens vaccine is obtained through preparation.The product produced through the preparation method is stable in yield, good in reproducibility and high in anti-tumor effect and spleen activity, and all other indexes meet the requirements of the quality standard.The serratia marcescens vaccine has obvious prevention and treatment effects on various solid tumors, and is an inactivated vaccine which is safe and free of toxic and side effects.