Abstract: During corn growth period, the species and population of main pests and their natural enemies were investigated regularly in field to evaluate the effects of phytase transgenic maize on their population dynamics. The results showed that the population dynamics of main pests and their natural enemies in phytase transgenic maize field were consistent with that in the field of its non-transgenic parent Liyu 35 and local corn variety Zhengdan 958. At most of corn growth stages, no significant differences were observed among the density of pests and natural enemies in the three treatment plots. Furthermore, the stalk inspection on the numbers of holes and worms of corn borer was conducted during harvest, the results also showed that there was no significant difference. So in the short term, the phytase transgenic maize had no effect on the population dynamics of main pests and their natural enemies in cornfield.