[Objective] The influence of different forest ages on the soil moisture dynamics and time stability of different slopes during the growing season (April-September) was determined in order to provide a scientific basis for the rational use of Cerasus humilis in the comprehensive management of small watersheds in hilly and gully areas of the Loess Plateau. [Methods] Based on long-term positioning observations of soil moisture in standard runoff plots with different slopes, the relevant parameters of soil moisture were calculated and analyzed using Origin Pro software. [Results] ① Soil water storage decreased after tree planting, but the decrease was not significant. There was a gradual recovery trend, but differences in soil water storage on different slopes were not significant. ② During the growing season, soil water contents in the 0-40 cm layer and below 100 cm in the 5° and 10° slope plots were low, and the coefficient of variation showed weak variation. Soil water storage in the 40-100 cm soil layer was high, and the coefficient of variation showed moderate variation. Soil water storage in the 0-100 cm layer for the 15° slope plot exhibited a large difference between the two study years. The soil water content below 120 cm was high and exhibited medium variation. ③ The temporal stability of soil water gradually increased with increases in the growth and age of Cerasus humilis, and were most obvious for the 15° slope plot. [Conclusion] The slope treatment model of “Cerasus humilis + level bench” has some advantages on slopes of less than 10° in hilly and gully areas of the Loess Plateau, depending on the growth status of Cerasus humilis.