Abstract: Based on the analysis of soil microbe and soil nutrients in different ecosystems of depression between karst hills, i.e., cropland, plantation forest, secondary forest, and primary forest, this study explored the characteristics of soil microbe and revealed the coupling relationships between soil microbe and nutrients. The composition of microbial population differed in the four ecosystems, where the ratio of fungi was lower in the four ecosystems. The ratio of actinomycetes in cropland, plantation and primary forest was larger than that of bacteria, while the reverse was true in the secondary forest. In the four ecosystems, the microbial biomass carbon (C_mic) was significantly correlated with the microbial biomass nitrogen (N_mic) and phosphorus (P_mic). The relationship between soil microbial factors and soil nutrients differed in the four ecosystems, among which the soil microbial biomass was closely with soil nutrients, while the amount of soil microbial population was weakly related with soil nutrient in the four ecosystems. This indicated that soil microbial populations such as bacteria, fungi and actinomycetes was randomly disturbed, instead of controlled by sole nutrient factor. The coupling relationships between soil microbe and soil nutrient factors were different in the four ecosystems. In the cropland, soil organic matter (SOM), pH, and total phosphorus (TP) played a greater role and mainly affected on C_mic, bacteria and fungi. In the plantation forest, soil water content, SOM, total nitrogen (TN), and TP had a greater effect on soil microbial biomass C, N, and P. In the secondary forest, pH, SOM, TP, available nitrogen (AN), and available potassium (AK) mainly influenced soil microbial biomass C, N, P, and fungi. In the primary forest, pH, TP, and AN proudly affected on soil microbial biomass C, N, P, and bacteria.