Abstract: To clarify the effects of protease inhibitors on the activities of midgut proteases in Callosobruchus chinensis (L.) larvae, the inhibitory effects of four kinds of protease inhibitors on the activities of midgut proteases of C. chinensis larvae were examined in vitro and in feeding conditions with indoor artificial insect inoculation. The activities of total protease, trypsin-like enzyme and chymotrypsin-like enzyme in the midgut of C. chinensis larvae fed on artificial mung bean that contained different contents of mung bean types in inhibitor (MBTI) were examined. The results showed that those four protease inhibitors had significant inhibitory effects on the activities of total protease, trypsin-like enzyme and chymotrypsin-like enzyme in C. chinensis larvae. The inhibitory effect was more significant when the concentration was higher. Among those inhibitors, the inhibitory effect of 20 μg·mL^-1 MBTI on three kinds of enzyme activities was the strongest, with reduction of 62.5%, 41.2% and 38.7%, respectively. Ovomucoid inhibitor (OI) had the lowest inhibitory effect. The activities of three enzymes in the midgut were also inhibited by C. chinensis larvae fed with artificial mung bean containing different inhibitors. The activities of three enzymes increased with the prolongation of the instar after feeding, but they were significantly lower than that in control. The inhibitory effect of MBTI was the strongest. The inhibitory effect on the activities of total protease and trypsin-like enzyme was gradually enhanced with the increases of MBTI contents when C. chinensis larvae were fed with artificial mung bean with different contents MBTI. The inhibitory effect on chymotrypsin-like enzyme activity was not significant. When the content of MBTI was up to 20%, the activity of chymotrypsin-like enzyme was obviously inhibited.