Abstract: Micromelalopha troglodyta (Graeser) is one of serious defoliators of poplars. In order to explore the occurrence regularity of emergence and reproductive behavior of M. troglodyte, which could provide references to the application of ecological control techniques, the circadian rhythms of emergence, calling, mating and oviposition were studied at (27±1) ℃ and (60±10)% RH under a 14L:10D photoperiod. The results showed that the emergence peak of the female occurred at the 7th day of the pupal stage, while the male at 8th day. As for the circadian rhythm during 24 hours, most individuals of both sexes emerged from the 6th hour of the photophase to the 2th hour of the scotophase. The 11th hour after initiation of the photophase was the emergence peak of female, while that of the male was 1 hour later. Female M. troglodyte after emergence did not call until the scotophase. The calling percentage reached the peak at the 6th-7th hour of the scotophase which increased with age of 1-3 days and reached 69.8% at the 3rd day, and then went down gradually. In the cage of only a pair of female and male, adults started mating after the 5th hour of the scotophase, and reached peak at the 7th-8th hour. But in the cage of multiple pairs of adult moths, they started mating after 0.5 hour of the scotophase, and the peak was 1.5 hours later than one pair’s. Eggs laid by females at the age of 1 to 3 days accounted for 68.4% of their total lifetime fecundity, and then the oviposition gradually reduced with the age.