Abstract: The starter mixture of Aspergillus oryzae and Aspergillus niger were used to produce Douchi and the protease activity and amino nitrogen content were respectively used as the indexes to explore the parameters of koji- making and fermentation by single factor test. The results showed that one good conditions of koji- making were as follows: 15 g fungus powder in 1 kg soybean,Aspergillus oryzae∶ Aspergillus niger = 4 ∶ 1,30 ℃,75% RH and duration of 48 h,under these conditions,the protease activity reached 1033 u / g. One good conditions of fermentation were as follows: 500 m L water and 50 g salt in 1 kg koji,45 ℃,65% RH and duration of 11 days,under these conditions,the amino nitrogen content reached 2.1 g /100 g.