Field insect population survey indicated that the principal natural predation enemies of cotton bollworm (Helicoverpa armigera Hubner) were Eringonidium graminicola Sundevall, Adonia variegata Goeze, Nabis sinoferus Hsiao. The results from experiments showed that the amount of prey consumed of these principal natural enemies increased when the density of prey rised, and decreased when the density of natural enemies increased. The predation function response fitted Holling's predation response equation II, and could be fit with the Disk Equation.