Abstract: In order to make better use of Trichogramma dendrolimi to control corn borer in the field, 7 treatments about the times and the period of releasing Trichogramma dendrolimi were set in Shuangcheng District, Harbin City and Liming Town, Zhaodong City.And the effects of Trichogramma dendrolimi release times and period on the parasitic rate, field control effect of Asian corn borer and the yield of corn were analyzed.The results showed that, all the treatments had significant effect to control the corn borer.Released three times Trichogramma dendrolimi had the best control effect, the control effect of two test sites was 80.5% and 83.3%,respectively, which was significantly higher than other treatments.The first two times release Trichogramma dendrolimi control effect of corn borer was significantly higher than the last two times released.The yield of maize with three times release Trichogramma dendrolimi was higher than other treatments, but no significant difference to the two times treatments.Based on the analysis of the control effect, cost and yield, the first two times released Trichogramma dendrolimi and released again to control the second generation of corn borer on August 2^nd,and the amount of each release time was 8 000 Head·（667 m~2）^-1,which can achieve good control effect of corn borer and maximize economic benefit.