Soil and grassland vegetation are important components for the grassland ecosystem, and they affect each other closely. The effect of grassland vegetation degradation on soil water holding capacity is a key problem for the research on grassland ecology, which is of great theoretical and practical importance to revealing the changes of water conservation function. In this study, the Tanggula Town of Golmud City in the headwaters area of Yangtze River was selected as the study area. The characteristics of soil water holding capacity in different grassland vegetation degradation stages were analyzed using soil sampling and lab analysis methods, and the effects of grassland vegetation degradation on soil water holding capacity were also discussed. Four important conclusions were obtained according to this research, listed as follows: (1) In the same grassland vegetation degradation stage, the changes of capillary water capacity, saturated water content and field water capacity depending on soil layers of different depths were similar. Moreover, in the same soil layer, the changes of the capillary water capacity, saturated water content and field water capacity depending on different grassland vegetation degradation stages also showed similar tendency. (2) In the same grassland vegetation degradation stage, the soil water holding capacity decreased as the increasing of soil layer depth in general. Especially in the nondegraded stage, the capillary water capacity, saturated water content and field water capacity in the soil layer of 10-20 cm depth decreased by 12.38%, 33.73% and 7.64% respectively, compared to those in the soil layer of 0-10 cm depth. (3) In the soil layer of the same depth, the capillary water capacity, saturated water content and field water capacity declined as the vegetation coverage degraded. Especially in the soil layer of 0-10 cm depth, the capillary water capacity, saturated water content and field water capacity in the slight degradation stage decreased by 41.52%, 59.95% and 27.03% respectively, compared to those in the nondegraded stage. (4) Soil water holding capacity significantly related to the soil bulk density, organic matter, total carbon, and total nitrogen. The characteristics of capillary water capacity, saturated water content and field water capacity in the different grassland vegetation degradation stages and soil layers might closely related to the changes of bulk density, organic matter, total carbon, total nitrogen and so on, which were induced by the landcover, biomass amount, distribution characteristics of plant roots on the earth surface. The theories, methods and technology system applied in this study can also provide experience for other headwater regions or similar research. These important conclusions could not only build a deep understanding for the relationship between grassland vegetation degradation and soil water holding capacity, but also provide the basis for the research of ecological environment and water resources in the headwaters area of Yangtze River.

Key words：soil water holding capacity; grassland vegetation degradation; headwaters area of Yangtze River; effect