The contents of soil mechanical composition, organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) of the soils from dam of Huabaowan landslide reservoir were investigated using systemative analysis. The density of bacteria, fungi and actinomycetes in the soils was measured using phospholipid fatty acids (PLFAs). We focused on the correlations of the density and community structure of microbes with the contents of carbon, nitrogen and mechanical composition of the soils from Huabaowan landslide reservoir which is formed naturally in the Loess Plateau. The results showed that: 1) The contents of sand decreased gradually, however, the contents of silt and the clay increased gradually along the direction from the tail of dam to the front of dam, and it was formed 5 distinct depositional cycles (0–40, 50–60, 70–80, 100–120, 240–260 cm) in the vertical direction; 2) Soil microbes mainly contained fatty acids (15:0 iso, 18:1 w9c, 18:1 w7c, 16:0 10-methyl) in landslide reservoir, which was about 54% of total PLFA. Bacteria was the main composition of the soil microbial community, accounting for 65%–75% of the total PLFA. Actinomycetes accounted for about 15%–25%, and fungi accounted for about 5%-10% of the total PLFA; 3) The changing tendency of diversity indices for the three species was similar, following the order: A profile >B profile >C profile. There were significant differences of soil microbial community structure among three profiles, and A profile differentiated more obviously than others; 4) The total soil microbes and the density of bacteria and fungi were positively correlated with the contents of silt, clay, MBC, MBN, SOC and TN significantly (P<0.05); 5) Fine particle components may be the main factor determining the density and community structure of microbes in the soils.