Based on the precipitation data of 160 gauge stations in China from 1979 to 2008, CMAP precipitation data provided by NOAA and NCEP/NCAR reanalyses, simulating with NCAR CAM51 model driven by global sea surface temperatures, the interdecadal variability of summer rainfall in South China and its relationship with South Asia High (SAH)is discussed in this study.Results show that summer precipitation in southern China and the eastward ridge point of SAH exhibit an obvious interdecadal change around the early 1990s and they are closely related each other. During the 1993—2008 (1979—1992) period, the position of SAH extended westward (eastward), and the Northwest Pacific subtropical High eastward (westward), bringing a convergence (divergence) anomaly at the lower troposphere and adivergence (convergence) anomaly at the upper troposphere over the South China, which caused a rising (sinking) motion and thus resulted in more (less) precipitation than normal in this region. These observed results are also verified by the numerical experiment results.