The analysis of temporal stability of soil moisture was a theoretical basis for obtaining accurate and reliable tempo-spatial distribution patterns of soil moisture and predicting the regional soil moisture. The volumetric soil moisture dynamics at different soil depth (0—20 cm, 0—40 cm, and 0—60 cm) on a Larix principis-rupprechtii plantation slope was measured by TRIME-PICO from May to November in 2015 in the small watershed of Xiangshuihe of Liupan Mountains. The temporal stability of soil moisture was analyzed by the cumulative probability functions, relative differences and Spearman rank correlation coefficients. The results showed that the soil moisture had a moderate variability both in time and space, and the degree of variation decreased gradually with increasing thickness of soil layers. The variability of cumulative probability for thicker soil layers (0—40 cm and 0—60 cm) was lower than that of the 0—20 cm soil layer under both dry and wet conditions. The mean relative differences of the soil moisture for the soil layers of 0—20 cm, 0—40 cm and 0—60 cm ranged from (－43.5%)~（47.9%）, (－42.9%)~（49.9%）and (－46.9%)~（40.0%）, respectively. The standard deviation of the mean relative differences (SDRD) decreased gradually with the increasing soil layer thickness. The SDRD of 0—20 cm, 0—40 cm and 0—60 cm soil layer were 11.1%, 8.3% and 7.8%, respectively. The soil moisture of all 3 soil thicknesses studied had a higher Spearman rank correlation coefficient (bigger than 0.7) and with a significant correlation, suggesting a higher temporal stability existed for the soil moisture of all the soil thickness studies. The representative points of the mean soil moisture of different soil layer thicknesses on the Larix principis-rupprechtii plantation slope were determined based on the temporal stability characteristic of soil moisture. With these representative points, the mean soil moisture of different soil layer thicknesses of the whole slope could be easily estimated.