Mountainous areas are the priority for forest restoration in semiarid regions, with hillslopes serving as the basic units of mountains. Precipitation is the only water source in these regions, and the uneven distribution of hillslope soil moisture replenishment after precipitation determines vegetation survival and growth. Therefore, in this study experiments were performed on a hillslope in the Liupan Mountains, Ningxia Hui Autonomous Region, China, to quantify the unevenness of soil moisture replenishment. Soil water content (SWC) in the 0-60 cm layer and precipitation were monitored throughout the growing season in 2020 and 2021. The results showed that (1) Annual soil moisture replenishment was the highest at the mid-slope position, with an average of 309.9 mm, especially under moderate and heavy rain grade conditions, reaching 38.7% and 30.8% of the total replenishment, respectively; (2) Vertical replenishment played a dominant role in the total replenishment, accounting for 82.8%; lateral replenishment played an important but lesser role, accounting for up to 17.2% of the total replenishment; (3) Based on a soil moisture replenishment model established in this study, the maximal replenishment occurred at 90 m from the top of the slope; (4) The dominant factors contributing to the soil moisture replenishment were rainfall amount and saturated hydraulic conductivity (Ks). These findings suggest that attention should be given to both vertical and lateral soil moisture replenishment, and the mid-slope position could be preferred for site selection to achieve precise and integrated forest-water management on hillslopes in semi-arid mountainous regions.