Study on the decomposition of 12 kinds of forest defoliation and the role of soil animals in Pinus koraiensisbroad-leaved mixed forest and spruce-fir of Xiao Hinggan Mountains.The method of eliminating the role of soil animals of different groups from different mesh decomposition bags was adopted.The results show that the decomposition efficiency of the defoliation is large mesh > small mesh >check, that is to say the role of large-type and middle-small-type soil animals and microorganism > the role of middle-small-type soil animals and microorganism > the role of microorganism only.The average decomposition efficiency of three years is 28.9%(large mesh), 28.2%(small mesh) and 26.2%(check mesh).By the end of the third year, the degree of decomposition of three kinds of mesh bags is 86.7%(large mesh), 84.6%(small mesh) and 78.7% (check mesh). The decomposition of latifoliate defoliation is entirely higher than conifer defoliation in three kinds of mesh bags.In latifoliate defoliation, the decomposition degree of Phellodondron amuriensis,Fraxinus mandshurica,Ulmus laciniata,Juglans mandshurica andAcer mono is the highest.But in conifer defoliation, the decomposition degree of Pinus koraiensis is the highest.From the decomposition of 12 kinds of defoliations in 3 years, the decomposition of defoliation is effected not only by large-size soil animals but also by middle-small-size soil animals, but the degree of function is different.In the prophase of decomposition, the role of soil animals was gradually increasing and the biggest value appeared in October of the second year.Subsequently, the sole of soil animals was decreasing, and the role of large-type soil animals > the role of middle-small-type soil animals.The role of soil animals is different when the kind of defoliation and the time of decomposition are different.