Abstract: Results of an analysis show that during the recent 50 years there is an evident correlation between the precipitation of Yunnan and the sea surface temperature (SST) over the eastern equatorial Pacific. For example,a strong positive correlation appears between the previous SST and the autumn precipitation of Yunnan,whereas there is a strong negative correlation between SST and the earlier summer precipitation. It shows that in the years of El Nino (La Nina),the earlier summer precipitation of Yunnan is less (more) than normal but the autumn precipitation is more (less) than normal and the rainy season of Yunnan begins later (earlier) than normal. So in our opinion,this is the main influence of ENSO events upon Yunnan precipitation and it also associates with some characteristics of interdecadal variation. For instance,the correlation between the precipitation of Yunnan and SST is remarkable during the period from the middle of 1970's to the end of 1980's,but the correlation is weak out of this period.