Seven soils with a large range of soil organic carbon and nitrogen were fractionated according to particle size by ultrasonic dispersion and sedimentation, then the distribution of soil C, N, P and K in the clay, silt and sand fractions was determined. At the same time, the availability of N in each fraction was also studied.The results showed that the C and N contents and their percentages in the soil organic C and N decreased with the increase of particle size, but the C/N ratio increased with the increase of particle size. The availability of N in <2μm fraction was highest and decreased with increase of the particle size.Soil P was mainly distributed in the fine fractions on the acidic soils, however on the calcareous soils in the coarser fractions.The exchangeable and non-exchangeable K was concentrated on the <50μm fractions, indicating these fractions were the important K source to plant in the soil.