The invention discloses a method for preparing bacteria liquid for Riemerella anatipestifer vaccine, which comprises the propagation and identification of the first-level seed, and the propagation and fermentation of the second-level seed; the propagation and identification of the first-level seeds comprises the following steps of: inoculating freeze-dry basic microbial strain into the nutrient broth containing 10 percent of fetal bovine serum, and culturing the nutrient broth for 24h at the temperature of 37 DEG C; inoculating the obtained product onto the nutrient agar plate containing 10 percent of fetal bovine serum by streaking, then culturing the obtained product in the environment containing 5 to 10 percent of CO2 or candle jar for 24h to 48h at the temperature of 37 DEG C; after that, selecting several typical colonies, inoculating the typical colonies onto the nutrient agar slant containing 10 percent of fetal bovine serum, culturing the product in the environment containing 5 to 10 percent of CO2 or candle jar for 24h at the temperature of 37 DEG C, and obtaining first-level seeds; the propagation of the second-level seeds comprises the following steps of: inoculating the first-level seeds into the nutrient broth containing 10 percent of fetal bovine serum; and culturing the nutrient broth for 24h at the temperature of 37 DEG C; sampling the obtained product for pureness test; and if obtained product is tested to be qualified, keeping the product at the temperature of 2 to 8 DEG C, wherein the service life thereof is not more than five days, the culture medium used in the fermentation is the N-J synthetic medium containing one percent of lysed whole blood, the fermenting microbial strain is inoculated in an amount which is 2 percent based on that of the second-level seed liquid, the fermentation manner is liquid fermentation and culture in a culture tank, and the culture condition is continuously culturing 24h at the temperature of 37 DEG C.