The potential predictability of climatological mean circulation and the interannual variation of the South China Sea summer monsoon (SCSSM) were investigated using hindcast results from the Institute of Atmospheric Physics Dynamical Seasonal Prediction System (IAP DCP),along with the National Centers for Environmental Prediction (NCEP) reanalysis data from the period of 1980-2000.The large-scale characteristics of the SCSSM monthly and seasonal mean low-level circulation have been well reproduced by IAP DCP,especially for the zonal wind at 850 hPa;furthermore,the hindcast variability also agrees quite well with observations.By introducing the South China Sea summer monsoon index,the potential predictability of IAP DCP for the intensity of the SCSSM has been evaluated.IAP DCP showed skill in predicting the interannual variation of SCSSM intensity.The result is highly encouraging;the correlation between the hindcasted and observed SCSSM Index was 0.58,which passes the 95% significance test.The result for the seasonal mean June-July-August SCSSM Index was better than that for the monthly mean,suggesting that seasonal forecasts are more reliable than monthly forecasts. The potential predictability of climatological mean circulation and the interannual variation of the South China Sea summer monsoon (SCSSM) were investigated using hindcast results from the Institute of Atmospheric Physics Dynamical Seasonal Prediction System (IAP DCP), along with the National Centers for Environmental Prediction ( NCEP) reanalysis data from the period of 1980-2000. Large-scale characteristics of the SCSSM monthly and seasonal mean low-level cycles have been well reproduced by IAP DCP, especially for the zonal wind at 850 hPa; also agrees quite well with observations. By introducing the South China Sea summer monsoon index, the potential predictability of IAP DCP for the intensity of the SCSSM has been evaluated. IAP DCP showed skill in predicting the interannual variation of SCSSM intensity. The result is highly the correlation between the hindcasted and observed SCSSM Index was 0.58, which passes the 95% significance te the result for the seasonal mean June-July-August SCSSM Index was better than that for the monthly mean, suggesting that seasonal forecasts are more reliable than monthly forecasts.