Glutathione S-transferases (GSTs) and carboxylesterases (CarEs) play important roles in the detoxification of endogenous and exogenous compounds. In this study, the biochemical effects of dietary cadmium (Cd) on the activities of GST and CarE in different developmental stages of the rice grasshopper Oxya chinensis Thunberg were studied. The results showed that the effects of the Cd concentration and developmental stage on GST activity were statistically significant. GST activity in O. chinensis increased at the highest Cd concentration in most nymphs, suggesting that GST is typically inducible by Cd. However, GST activity was inhibited in adults under Cd stress owing to life-stagespecific physiological characteristics. The results showed that the substrates, developmental stage, and Cd concentration had statistically significant effects on CarE activity. In most studies of CarE activity, the interaction between any two studied factors was statistically significant, although the interaction effects of the substrates, developmental stages, and Cd concentrations were not significant, which implied that the insect physiological condition and the external environmental may affect CarE activity. The results suggest that the insect's life stage and enzyme substrates should be considered when enzyme activity under Cd stress is studied.