Mediums and protective agents of Bifidobacterium were screened for maximum viable count,which was the best to obtain maximum viable counts for Bifidobacterium bifidum BB-G90.Growth parameter of B.bifidum BB-G90 were confirmed by fermentation with controlled pH value of 5.0±0.5.Results of the research showed that medium No.3 was the best and the most appropriate protective agent of B.bifidum BB-G90 was No.3.With controlled pH value of 5.0±0.5 the viable cell number of B.bifidum BB-G90 could reach 1.80×109 CFU/mL in the optimal growth medium at 37℃ for 22 h under anaerobic condition.Living bacteria content of B.bifidum BB-G90 powder were 4.10×1011 CFU/g after freeze-drying.