Developmental time and sex ratio of Diadegma semiclausum, a larval parasite of diamondback moth, Plutella xylostella L. were observed under six constant temperatures ranged from 15[degree]C to 30[degree]C. Results of Guangdong showed that the developmental time from egg to adult decreased significantly with the increase of temperature at 15 - 27[degree]C, the developmental time of whole generation were 35. 97, 21.75, 18. 57, 15.38, 14. 93 d at 15, 20, 22, 25, 27[degree]C, respectively ; the temperature threshold for the whole generation was calculated to be 7. 53[degree]C, and the effective temperature sums for the whole generation was assessed as 269. 07 degree day ; There was no effective of temperature on the sex ratio ([female] : [male]) at 15 - 25[degree]C, but when temperature was higher than 25 [degree]C, the sex ratio ([female] : [male]) decreased significantly, 0. 25 at 27[degree]C . The optimal temperature for mass - rearing was 22[degree]C. zongqichen55@163.com noneEmail20150314