Abstract: Studying annual climatological jump of SST in northern Pacific by means of the method of moving T test,an obvious climatic jump is indicated to be present late 1970's through early 1980's and there are significant difference befor and after the jump in terms of its SST structure and evolutionary processes of El Nino event.The discovery is then based to study the effect of the jump on rainfall in June-August floods season in China,concluding that the season precipitation is less(more) than usual in the northeast of China and Changjiang River Basin(north and south of China) before the jump and vice versa.