[Objective] The soil particle size characteristics of different vegetation types on the southern slope of Qilian Mountain were analyzed in order to provide a scientific basis for the sustainable use of regional soil resources and ecological environment protection.[Methods] 75 samples were collected and measured from different vegetation types on the southern slope of Qilian Mountain by Mastersizer 2 000 laser particle size analyzer. Then the parameters of particle size were calculated by using Fokker and Ward formula and performed one-way ANOVA.[Results] ① Picea crassifolia, Juniperus przewalskii and alpine meadows were of silt-clay(< 63 μm) grade, mixed shrubs and alpine grassland were of sand grade(> 63 μm). The size of the forestland soil was finest and the alpine meadow was followed in composition of size. Mixed shrubs and alpine grassland showed degradation trend, and had coarser grain composition than those of forestland and alpine meadow. ② The mean grain size of different vegetation types was Picea crassifolia(6.15Ф) > Juniperus przewalskii(5.81Ф) > alpine meadow(5.22Ф) > mixed shrub(5.07Ф) > alpine grassland(5.04Ф). The sorting coefficient of different vegetation types was alpine grassland(2.65) > alpine meadow (2.45) > mixed shrub (2.33) > Picea crassifolia(2.17) > Juniperus przewalskii(2.11). The skewness of different vegetation types was alpine meadow(0.19) > alpine meadow(0.12) > mixed shrub(0.035) > Picea crassifolia(0.032) > Juniperus przewalskii(-0.05). The kurdishness of different vegetation types was Picea crassifolia(0.968) > mixed shrub(0.966) > Juniperus przewalskii(0.929) > alpine meadow(0.887) > alpine grassland(0.867). ③ There were some similarities and differences in frequency curves of different vegetation types. The peak shape of forestland and shrubs was nearly symmetrical and unimodal. The peak shape of alpine meadow and alpine grassland was multi-peaked and the fact indicates that grassland was greatly disturbed by external factors and sources were mixed.[Conclusion] In the case of natural environmental impact and high human activity intensity, the grain size of alpine meadows and alpine grasslands would be further coarsened, and the risk of desertification is the greatest, which is the type of vegetation that is relatively urgently needed for conservation in this area.