Abstract: In order to compare and objectively evaluate the cellulase activity in different intestinal segments, the activity of three types of cellulase in three segments (foregut, midgut, hindgut) of Cyrtotrachelus bugueti adult were measured at different pH and temperatures. The results showed that (1) there was a complete enzyme system in the intestinal tract of C. bugueti adults; (2) the C_X enzyme in the foregut of C. bugueti adults had a wider adaptive range of temperature and pH, and had greater stability; (3) the optimal temperature (T) was 50~70 ℃, and the optimal pH was 6~8. No enzyme activity was detected under high temperature and strong alkali conditions, and C₁ enzyme in the foregut had the maximum enzyme activities of 0.0349 mol·Min⁻¹·Mg⁻¹ (pH=3, T=40 ℃) compared with the other two segments; (4) the adaptation range of C₁ enzyme in the midgut was much larger than that of the other two segments. The optimum temperature was 30~70 ℃ and the optimum pH was 5~8. No enzyme activitiy was detected under strong acid and strong alkali conditions; (5) the optimum temperature range of the three enzymes in hindgut was 30~50 ℃, and the optimal pH range was 5~8, which was narrower than the optimal temperature and pH range of foregut and midgut of C. bugueti adults.