In order to effectively prevent soil erosion in the watershed and maintain ecological security, based on the daily precipitation data from 1982 to 2019 in Jiuqushui watershed, the inter-annual variation rules of erosivity of moderate rain, heavy rain, rainstorm and annual rainfall were analyzed by using wavelet analysis and cross wavelet transform, the influences of Sunspots, El Niño-Southern Oscillation (ENSO), Arctic Oscillation (AO) and Pacific Decadal Oscillation (PDO) on them were discussed. The results indicated that:(1) The inter-annual variation trend of moderate rain erosivity, heavy rain erosivity, rainstorm erosivity and annual rainfall erosivity was not significant (p>0.05), and the coefficient of variation (C_V) was 0.24, 0.31, 0.64 and 0.26, respectively, which were all moderate variations. (2) The periodic variation of rainfall erosivity in different magnitudes was obviously different, the annual rainfall erosivity and rainstorm erosivity had a 15 to 23 years cycle and a 19-year main cycle, which were more closely related. (3) The annual rainfall erosivity and rainstorm erosivity had significant resonance periods of 9 to 11, 10 to 11, 10 to 11 and 9 to 10 years with Sunspot, ENSO, AO and PDO, respectively. The impact of Sunspot, ENSO and PDO on rainstorm erosivity was greater than that of moderate rain erosivity and heavy rain erosivity. And the impact of AO on heavy rain erosivity was greater than that of moderate rain erosivity and rainstorm erosivity. The research results could provide scientific basis for soil erosion prediction and prevention in southern Jiangxi and even China.