Abstract: In the paper,Mucor racemosus was used as the main strain to explore the effect of fermentation on the nutrition and flavor of soybean meal,the fermentation with Saccharomyces rouxii and soybean meal ultrasonic pretreatment on the quality of M. racemosus fermented soybean meal. The results showed that the fermentation with M. racemosus could significantly increase the neutral protease activity,soluble protein content,sensory quality,total amino acid and free amino acid content of soybean meal,and effectively reduce the activity of trypsin inhibitor. After fermentation at 28 ℃ for 60 h,protease activity and soluble protein content of each fermented soybean meal reached the maximum value. Compared with unfermented soybean meal,protease activity of soybean meal fermented by M. racemosus was 1032.4 U/g,and the contents of soluble protein,total and free amino acids increased by 3.16 times,13.64% and 5.65 times,respectively. Trypsin inhibitor activity decreased by 84.57%. Both soybean meal ultrasonic pretreatment and the fermentation with S. rouxii were beneficial to the improvement of quality of the fermented soybean meal. Among them,content of trypsin inhibitor in S4(Coupling fermentation by M. racemosus and S. rouxii after ultrasonic pretreatment)decreased from 4375 to 350 U/g,decreased by 92%.Free amino acids content increased by 7.69 times,and total amino acids content increased by 22.92%,which effectively improved nutrition and sensory quality of soybean meal,and provided guidance for further research and application of soybean meal.