Abstract: This experiment was based on traditional microbiological methods for natural mold morphology analysis of fermented bean paste, delving into the law of the molds change by natural fermentation, exploring the mold components and the dominating ones in the traditional soybean fermentation, which played a key role for the sauce fermentation. In this paper, the mold in the bean paste sample of different fermentation time were counted and separated, and identification by the slide culture method. Six representative strains were isolated from the traditional fermentation bean paste by using traditional cultivation and further to identify by fungi wet chamber culture method, determining the species status, respectively: Aspergillus oryzae, Mucedo, Absidia, Mucor racemosus, Actinomucor elegans, Aspergillus and Aspergillus oryzae became the dominating one. This study revealed the mold components in the process of the bean sauce fermentation, which would provide the basis from the traditional preparation to factory production.