Strongly impacted by climate change, glacier and snow, as major parts of solid reservoirs in mountains, can regulate the local water sources. This study uses glacier and snow datasets to analyze the variations of glaciers, snow, water storage, and runoff in the Tianshan Mountains, and selects three typical river basins (Aksu River, Kaidu River, and Urumqi River) to interpret the impact of glacier and snow changes on regional water resources in this region. Results indicate that: (1) the functional relationship between glaciers retreat and glaciers area is f(x) = -0.53*x~(-0.15) (R~2 = 0.42, RMSE = 0.086), and small glacier retreat is more sensitive under climate change. Meanwhile, glacier retreat rate at the low-middle elevation bands is faster than that of the high elevation band; (2) the decreasing rate of regional average total water storage (TWS) is -0.71.53 cm/a in the study area during 2003-2015. The maximum of TWS deficit region was mainly observed in the central part of the mountains, which is closely related with accelerated glacier retreats; (3) during the past half century, the increased melting of glacier and snow melt led to a runoff increase in the three typical river basins, especially in the Aksu river basin (0.4*10~8 m~3/a). The area decreasing, thinning, and rising equilibrium line altitude (ELV) of glaciers are the major factor contributing to the decreasing trend of runoff in the three river basins since the mid-1990s. Therefore, results revealed that the mechanism of influence of solid water reserves reduction in mountains on regional water resources under climate change, and also provided references for water resources management in the mountainous river basin.