[Objective] The spatiotemporal variation characteristics of different magnitudes of rainfall erosivity in Xiangshui River basin of Southern Jiangxi Province were determined, in order to provide an important scientific basis for soil erosion prevention and ecological environmental management in the basin. [Methods] Taking Xiangshui River basin in Southern Jiangsu Province as the research object, the Zhang Wenbo daily rainfall model was used with comparative analysis of rainfall erosivity to select the optimal interpolation method among ordinary Kriging interpolation (OK), inverse distance weighted interpolation (IDW), and radial basis function interpolation (RBF). The spatiotemporal variation characteristics of rainfall erosivity was analyzed in Xiangshui River basin. [Results] ① IDW was more suitable than OK and RBF in Xiangshui River basin. ② The spatial distribution differences of rainfall erosivity and annual rainfall erosivity of different magnitudes in Xiangshui River basin from 1984 to 2021 increased with the increase of magnitude, and both showed an overall trend of higher values in the north and south, and lower values in the central region. ③ The coefficients of variation of the erosion force of annual rainfall, moderate rain, heavy rain, and rainstorm in Xiangshui River basin from 1984 to 2021 were 0.26, 0.15, 0.25, and 0.47, respectively, all of which were classified as moderate variations, and the interannual variation trend was not significant. The magnitude of rainfall erosion force of different magnitudes, the proportion of annual rainfall erosion force, and the interannual change rate increased with the increase of magnitude. The oscillation cycles were basically the same, all of which were 3~4 oscillation cycles. [Conclusion] The northern part of the basin is a region with high possibility of soil erosion. Strengthening soil and water conservation measures in this region according to local conditions will help prevent and control soil erosion in the Xiangshui River basin.