Abstract: Based on CN05.1 precipitation dataset and ERA5 reanalysis, the spatiotemporal variation characteristics and circulation feature of late spring (May) precipitation in Yunnan during 1961–2020 are analyzed by using various statistical methods, and the influence of the synergy between westerly wind and monsoon on late spring precipitation is discussed by using the synergy index. The results show that: In Yunnan, May is the month with the most precipitation in spring with a spatial distribution of precipitation decreasing from south to north. In addition, the precipitation shows a pronounced interannual variation, while the spatial climate trends are not significant. In comparison with the individual westerly wind and monsoon indexes, the westerly-monsoon synergy index has a better indication for May precipitation in Yunnan, the correlation and the same sign rate between the synergy index and extreme precipitation are higher. Composite analysis of circulation field also implies that when the westerly-monsoon synergy effect enhances (weakens), the air flow over Yunnan is dominated by divergence ( convergence ) due to the influence of the abnormal high ( low ) pressure in the Arabian Sea, which is conducive to ascending (descending) motions. Meanwhile, cyclonic (anticyclonic) anomalies dominate over the Bay of Bengal at the middle and lower troposphere, strengthening (weakening) the water vapor transport towards Yunnan, and eventually causing more (less) precipitation in Yunnan.