Objective: To reveal processing mechanism of Sojae Semen Praeparatum by monitoring dynamic change of microbe species in its fermentation process. Method: Biolog microbial identification system was used to identify dominant bacteria

moulds and yeasts

which isolated from Sojae Semen Praeparatum at different fermentation time points of fermentation process. Result: Bacillus subtilis was dominant bacterium in the whole fermentation process.Dominant microorganisms were B. subtilis

B. amyloliquefaciens

Aspergillus flavus

A. parasiticus and Debaryomyces hansenii C in the 3 th day of fermentation.Dominant microorganisms were B. subtilis

Staphylococcus sciuri

Acinetobacter radioresistens

Enterococcus casseliflavus

A. parasiticus

D. hansenii C

Rhodotorula acheniorum and Trichosporon beigelii A in the 6th day of fermentation.Dominant microorganisms were B. subtilis

Escherichia hermannii

A. niger and R. acheniorum in the 3 th day of 'secondary fermentation'.Dominant microorganisms were B. subtilis

Klebsiella oxytoca

Cryptococcus marinus and C. laurentii

no mould appeared in the 15th day of 'secondary fermentation'. Conclusion: Dynamic changes of microbial flora occurs in the whole fermentation process.B. subtilis is dominant bacterium in the whole process.