Little is known about the relationship between soil microbial communities and soil properties in southern boreal forests. To further our knowledge about that relationship, we compared the soil samples in southern boreal forests of the Greater Khingan Mountains-the southernmost boreal forest biome in the world. The forests can be divided into boardleaf forests dominated by birch (Betula platyphylla) or aspen (Populus davidiana) and coniferous forests dominated by larch (Larix gmelinii) or pine (Pinus sylvestris var. mongolica). Results suggested different soil microbial communities and soil properties between these southern boreal forests. Soil protease activity strongly associated with soil fungal communities in broadleaf and coniferous forests (p < 0.05), but not with soil bacterial communities (p > 0.05). Soil ammonium nitrogen and total phosphorus contents strongly associated with soil fungal and bacterial communities in broadleaf forests (p < 0.05), but not in coniferous forests (p > 0.05). Soil potassium content demonstrated strong correlations with both soil fungal and bacterial communities in broadleaf and coniferous forests (p < 0.05). These results provide evidence for different soil communities and soil properties in southern boreal forest, and further elucidate the explicit correlation between soil microbial communities and soil properties in southern boreal forests.