Abstract: Water is the primary factor limiting the growth of shrub plants in the arid and semi-arid regions of northwest China. Based on the stable isotope technique and multivariate linear mixing model (IsoSource) and proportional similarity index (PSI), this paper analyzed and compared the water use strategies of the shrub plants of Salix cupularis Rehd., Potentilla fruticosa Linn., Rhododendron thymifolium Maxim., and Salix oritrepha Schneid., and discussed their influencing factors. The aim of this research is to gain a deeper understanding of water use strategies of shrub plants and their influencing factors in the subalpine zone. Results showed that most shrub plants utilized soil water at a depth of 0-30 cm, although there were variations in the water sources and proportions used by shrub plants across different habitats during different growth periods. Additionally, the water competition among shrub plants across different habitats varied significantly (P < 0.01). During the early period of growing season (May-June, 2019), shrub plants exhibited intense competition for soil water on both the semi-sunny slope and the semi-shady slope habitats, with mean PSI values of 0.76 and 0.75, respectively. In contrast, during the middle and end periods of growing season (July-August and September-October, 2019), the intensity of water competition among shrub plants was significantly higher on the semi-shady slope habitat, with mean PSI values of 0.85 and 0.67, respectively, compared to the semi-sunny slope habitat, which had mean PSI values of 0.57 and 0.58, respectively. Transpiration and soil water content were identified as the primary factors influencing the water use strategies of subalpine shrub plants. These findings help explain how slope aspect and growth period mediate water-use differentiation and competition among subalpine shrubs and provide a basis for predicting their responses to changes in soil water availability.