Abstract: The integrated effect of the main predators (Erigone graminicollm, antheconidae furcellate, Pirata subpiraticus) on the common cutworm Spodoptera litura in coexistence system was studied, and the predation model of the predators was established by the rotational composite design of quadratic regression. The interference among species and the contribution of the 4 species to the predation on the pest population could be comprehended by analyzing the predation model. The principal efficiency analysis on this model indicated that the density of the common cutworm was the greatest on the total predation rate of the predators. Among the 3 predators, E.graminicollm had the greatest effect on predation, and C.furcellate, P.subpiraticus had less effect. The interaction between the species indicated that P.subpiraticus would kill seriously E.graminicollm, and C.furcellate, however, E.graminicollm and C.furcellate could promote each other, and increased the predation as the densities of the 2 predators increased.