Based on the observed station precipitation data over China in winter,the monthly Hadley Center Global Sea Ice and Sea Surface Temperature(HadISST) and the monthly reanalysis data provided by National Centers for Environmental Prediction-National Center for Atmospheric Research(NCEP/NCAR) from 1951 to 2010,the relationship between the western Pacific warm pool(WPWP) and winter precipitation over South China(SC) has been studied.The results show that the correlation between WPWP and winter precipitation over SC has obvious interdecadal transition in 1972.Before the 1970s,the negative correlation between them is weak and has not passed significance test.But the correlation between them has reached-0.5——0.6 after the 1970s.By the regression analysis,it is found that,before the 1970s,the effect of WPWP on water vapor and dynamic conditions that affect winter rainfall over SC is not significant,so its relation with winter rainfall over SC is not obvious.After the 1970s,when WPWP SST is warmer,an obvious cyclonic circulation has been aroused in the Philippine Sea area.The northerly wind over the northwest side of the cyclonic circulation is not favor of water vapor from South China Sea transported to SC,so the water vapor divergence over SC increases.The convection and perturbation over the southern branch trough region weaken significantly and the perturbation can not spread to the downstream region,which causes the weakened perturbation over SC.In addition,the warming of WPWP leads to remarkable increase of meridional circulation in the Northern Hemisphere,and the sinking branch is located in SC region,which strengthens the sinking movement over SC,so it results in the decreased rainfall over SC in winter,and vice versa.