The say sauce koji where made use of different kinds of seed koji were used to brewing of soysauce. The pure, complex and bacteria contaminated seed koji were used in this experiment, And the euzyme activity, Micrflora, chemical composition and TN-solubility ratio of each soysauce mash during the fermentation periods were measured respectively. The results obtained were as follows. 1. The neutral and alkali protease activity of each soysauce mash were decreassed in the process of fermentation period. In this case the activitities of protease in the bacteria contaminated koji were remarkably decreased. 2. The microflora in one ml of soysauce mash showed the tendency of increase in process of fermentation period. The increase in bacteria contaminated seed koji group was remarkable. 3. The content of total nitrogen, amino-N and ammonia-N in soysauce during the course of fermentation were increase. And alcohol, reducing sugar and pure extract contents in soysauce were also increased in the former stage of fermentation, but in the latter stage of fermentation decreased. 4. Though the content of ammonia-N in bacteria contaminated seed koji group was high, the pH value was low in comparison with the others. 5. Pure seed koji group were shown the most effective in the result of total nitrogen solubility ratio and sensual test, while the bacteria contaminated seed koji group was the worst.