[Objectives]  To explore optimum temperature on weight gain, food conversion efficiency and digestive enzyme activities of Tenebrio molitor larvae. [Methods]  The rate of approximate digestibility, body weight, conversion efficiency, and digestive enzyme activities of different larval instars of T. molitor were investigated under different temperatures. [Results]  The results showed that temperature had great influence on weight gain, approximate digestibility, and conversion efficiency. The weight of larval raised at 24℃ and 28℃ were significantly higher than that of raised at 20℃ and 32℃. At 28℃, the average daily weight gain of 60-day-old and 90-day-old larvae were 1.26 and 1.35 times greater than those 20℃, respectively. The approximate digestibility and conversion efficiency showed similar patterns with changing temperature conditions. In addition, temperature influenced the digestive enzyme activities of the larvae. The activity of intestinal protease, amylase, endo β-1, 4-β-glucan glycosidase (Cx), and β-glucosidase at 24-28℃ were all higher than 20℃ or 32℃. The activities of these digestive enzymes also varied with larval age. [Conclusion]  The optimal temperature of conversion efficiency and weight gain of T. molitor larvae were 24℃ and 28℃. The activities of 4 digestive enzymes statstically increases as the larvae grew older.