Soil samples were collected from woodland,rain-fed cropland,irrigated cropland and grassland in Wuchuan County,Inner Mongolia in early May of 2002 in the study on distribution characteristics of soil microbial phospholipid fatty acids(PLFAs).Soil microbial biomass carbon(MBC),PLFAs and some soil basic properties were determined.Results showed that total PLFAs ranged from 19.82 ng g^-1 to 47.28 ng g^-1,and monounsaturated fatty acids with G^- bacteria as indicator accounted for 29%~37% and branch fatty acids with G⁺ bacteria for 15%~20% of the total PLFAs.Irrigated cropland and grassland soils were significantly higher or nearly 3 times than rain-fed cropland and woodland soils in total PLFAs.Principal component analysis(PCA) indicated that PC1 consisted mainly of fatty acids of 14:0 3OH,cy19:0,12:0,br17:0 and 18:2 ω9,12,and PC2 mainly of 16:0,16:1 ω11,18:1 ω9,19:0 and a15:0.The irrigated cropland,rain-fed cropland and grassland were quite similar in microbial community structure,but significantly different from woodland soil.