Composition and structure of cropland soil fauna as affected by exogenous carbon and nitrogen was studied in the black soil area of Jilin in 2011, using Hand-sorting, modified Tullgren and Baermann’s methods. The field under study was designed to have seven treatments of exogenous carbon and nitrogen, separately, i.e. control (CK), exogenous carbon (C0.5, C1.0, C2.0) and exogenous nitrogen (N0.5, N1.0, N2.0). A total of 56 886 soil fauna individuals were obtained after 5 times of gathering during the crop growing season from May to September, and sorted into 79 families, 3 suborders, 23 orders, and 11 classes under 3 phyla, including 80 unidentified individuals. The data obtained show that the cropland soil fauna lived mainly in the 0～5 cm soil layer and decreased with soil depth in population; as compared with the control (CK), the treatments with exgenous carbon increased the number of individuals and groups of soil fauna in the field with a trend increasing with the concentration of exgenous carbon; and the treatments with exgenous nitrogen decreased the number of individuals of soil macro fauna, but increased the numbers of individuals of soil meso-and micro-fauna, showing a trend of the more the less and the more the more, respectively. During the crop growing season, cropland soil fauna rose in number of individuals and groups from May to August and then declined in September. Variance analysis of the data shows that the impacts of exogenous carbon and nitrogen on soil macro-, meso-and micro-fauna in number of individuals and groups were significant (p＜0.01); and the cropland soil fauna varied significantly in number of individuals and groups (p＜0.01) during the crop growing season. The numbers of individuals and groups of soil meso-and micro-fauna and the number of groups of soil macro-fauna were closely related with the concentration of nutrients released from exogenous carbon and nitrogen sources. Exogenous carbon favors guilds of soil fauna and diversification of the composition of the cropland soil fauna community.