The pattern of laying egg and progeny sex allocation of Microplitis mediator were studied in laboratory. The results showed that females could oviposit at the day of their emergence despite having mated or not. If they did not mate the female would make arrhenotokous parthenogenesis. Under the condition of temperature 22 [plus or minus] 1.5[degree]C, RH 40% -60%, light intensity 4700 - 51001x, the average life span 1. of females was 8.3 d, the average persisting time of egg-laying was 7 d and the longest time could reach 15 d. The average number of eggs produced by one female was 84.4 and the maximum number was 231. Number of eggs produced daily by one female was significantly related to the age of the female. From the 1st - 12th days, average number of eggs produced per day by one female was 7.8 - 17.4. Afterward the 1., number reduced to 1.3 - 5.0. The 90% female died after 15 d and the survivals could not oviposit any more. During the oviposition of M. mediator, daily sex allocation of the progeny decreased gradually. The sex ratio were 1.36 - 1.59:1 within the first 3 days, 0.79 - 1.12:1 within the 4th to 8th day, after 9th day, non-femal occurred. none