Abstract: Based on the precipitation data of 125 meteorological observation stations in Yunnan, NCEP / NCAR reanalysis atmospheric circulation and sea surface temperature (SST) of Hadley Center in England, the main precipitation patterns in Yunnan in May are analyzed. It is found that the North Pacific, the equatorial Middle East Pacific and the equatorial Indian Ocean are the three main key regions affecting precipitation in May in Yunnan. The PDO-like index, ENSO-like index, Dsst index and Esst index are defined, and the relationship between the main precipitation modes in May and SST anomaly (SSTA) in Yunnan is further analyzed. The results show that: (1) The main precipitation patterns include regional consistency and East-West difference, the East-West difference pattern displays obvious asymmetry when the precipitation in the East is more than that in the West, while the range of precipitation in the western region is small when the precipitation in the East is less than that in the West, mainly characterized by less precipitation in the middle and eastern region. (2) The PDO-like and ENSO-like SSTA modes in the North Pacific are the main factors affecting the consistent precipitation change in Yunnan. PDO-like mainly affects the change of water vapor transport, while ENSO-like mainly affects the cold air activity. That is, the SSTA is conducive to more consistent precipitation in Yunnan, and vice versa. (3) The equatorial Indian Ocean SSTA represented by the Dsst index is the main factor affecting the East-West difference in precipitation in Yunnan. When the Indian Ocean SSTA is positive, it is conducive to more precipitation in the West and less in the East. On the contrary, it is conducive to less precipitation in the West and more in the East in Yunnan. However, the equatorial Middle East Pacific SSTA represented by the Esst index will weaken the impact of the Dsst index on the East-West difference in precipitation, so that the precipitation in Yunnan tends to be consistent in the whole region.