Soil moisture is a critical determinant of tree growth in semi-arid regions. However, previous research has frequently overlooked the impact of soil moisture driving by hillslope water transport, a process of paramount importance in these landscapes. In this study, these effects were quantified by monitoring tree stem diameter, leaf area, meteorological conditions, and soil moisture along a larch hillslope in northwestern China during the growing seasons (May to October) of 2021 to 2023. The results demonstrate that the promotion effect of soil moisture replenishment (SMR) during the growing period (May to August) on larch growth varied substantially, which was ranged from 0.72 to 3.37 of leaf area index (LAI) and -0.01 to 0.23 cm3/m2 of basal area increment (BAI) in relatively wet year and ranged from 0.82 to 2.47 of LAI and -0.03 to 0.10 cm3/m2 of BAI in summer dry year. Furthermore, this promotion effect of SMR was more pronounced in stem growth than in leaf expansion. SMR also significantly altered water use efficiency (WUE), exhibiting a logistic relationship where WUE increased rapidly by 0.02 WUE/10 mm of SMR when the annual SMR ranged between 75 and 200 mm. Consequently, climate change, characterised by drier summer, is expected to reduce SMR during the growing period, further be detrimental to tree growth. These findings suggest that SMR should be regarded as a primary indicator for site selection and areas with an annual SMR exceeding 200 mm should be prioritised for ecological restoration in semi-arid regions.