As one of the seven major river systems in Zhejiang, the Yongjiang River Basin plays an important role in the construction of ecological civilization and regional high quality development in eastern Zhejiang. Based on three sets of land use, meteorology and soil data of the Yongjiang River Basin, the water supply capacity of different periods was estimated, and the topographic gradient effect of water yield was analyzed. The results showed that the land use types in the Yongjiang River Basin were mainly farmland and forest. The construction land expanded significantly, whereas the area of other land types decreased. The conversion between different land use types was frequent. The average total water yield in the basin was about 3.069×108 m3, showing a downward trend. The water yield in the upper and middle reaches of the Yongjiang River Basin was relatively high, such as the Yaojiang River Sub basin, Yinjiang River Sub basin and Shanxijiang River Sub basin, and the contribution of farmland and forest to the water yield of the basin was relatively high. The topographic index of the Yongjiang River Basin was mainly distributed in the first level, and the topographic gradient effect of water yield was significant.