Abstract: The mixed fermentation of Bacillus thuringiensis Ym2102 and Bacillus cerace DL5789 were investigated.The results show that the death rate of spodoptera exigua can reach 94.2% when the mixed fermentation was diluted in 3 000 times.The total bacteriain shaking culture is 2.8×10~9,and the vary of pH becomes slowly.