Abstract: In this paper the interannual variations of subtropic high ridge position over western Pacific in June are investigated by using the data of the ridge based on 500 hPa height from 1951 to 1991. The results indicate that 41-year averaged ridge position is located in 20°N, the oscillations of the ridge position exhibit 32-year, 5.3-year, 2-3year period and its variations are associated with 500 hPa height, SST of South China Sea and western Pacific. As the ridge locates more to the north (>20°N), there will be less precipitation in south of China, and as the ridge is more to south (<20°N), there will be much more precipitation.