Abstract:The diversity and numbers of soil microorganisms in different forest types were studied, as well as Shannon index (H), richness index of genera (S), Pielou evenness index (J) and Simpson index (D) in Ledum palustre —Larix gmelinii virgin forest, Herbage—L. gmelinii virgin forest, Betula—L. gmelinii virgin forest, clear cutting L. gmelinii forest and L. gmelinii forest burned areas in the national forestry ecosystems station of Inner Mongolia Great Xingan Mountains by selective media. The results showed that bacteria isolated from five plots belonged to 24 genera, Brevibacterium, Bacillus, Corynebacterium and Micrococcus were main genera; actinomycetes were classified into 6 groups, Flavus and Albosporus were the main genera; fungi were composed of 20 genera, Penicillium and Cephalosporium were the dominant genera. Diversity index (H), richness index of genera (S), evenness index (J) and dominant index (D) of soil microorganisms of Larix gmelinii varied with forest types; and the order of diversity index and richness index of bacteria followed LLV > HLV > LFB > CL > BLV, while actionmycetes were BLV > HLV > LLV > LFB > CL and fungi were CL > HLV > BLV > LFB > LLV.