In order to explore the effects of different seasons and vegetation types on the distribution of soil microbes, two vegetation types were used as research objects at different altitudes in Nanshan of Lanzhou, the seasonal dynamics of soil microbes were measured by the dilution-coated plate. The results showed that the number of bacteria accounted for 96.22%~99.80% of the total number of microbes in the study area, far higher than the number of fungi and actinomycetes. The soil microorganism groups showed significant difference with the seasonal variation. The total number of soil microbes showed the highest in summer with, 89.22×10⁶cfu/g soil, which were 12.02, 3.28 and 2.74 times in spring, autumn and winter respectively. The number of bacteria was the highest in summer, and the number of fungi and actinomycetes reached the maximum in spring. The amount of soil microorganisms in the plantations was slightly lower than that on the barren slopes, and the soil water content and organic carbon contents were higher than those of the barren slopes. With the altitude increasing, pH increased gradually, soil temperature, organic carbon and total nitrogen decreased gradually, and the total number of soil microorganisms decreased firstly and then increased. Correlation analysis showed that the correlation coefficients of microbial groups and environmental factors were different in different seasons. In spring, there was significant positive correlation between actinomycetes and organic carbon, and fungi and soil organic carbon and total nitrogen had a significant positive correlation (P<0.01) in autumn. Redundancy analysis showed that the highest correlation coefficient between organic carbon and the first species axis was 0.520, indicating that soil organic carbon content was the dominant factor affecting the distribution of soil microbial groups.