Abstract: Counter maps of the East China Sea and the adjacent northwest Pacific Ocean are compiled and analyzed based on the annual mean data, monthly average data, monthly difference and inter-monthly difference data of SODA surface salinity for the past 30-year climate reference period (1981-2010). The climatic distribution patterns of the surface salinity field in the Pacific Ocean have provided a solid foundation for further study of the long-term climate changes in the region. As it is observed that: (1) The average surface salinity in the study area gradually increase from northwest to southeast, with three distinct salinity subareas: the area of the East China Sea continental shelf, the part of East China Sea where the Kuroshio current passes through and the area of Northwest Pacific Ocean; (2) There is a significant cyclical change in the salinity of surface water in the study area, among which the periodicity of the minimum salinity is the most significant; (3) In terms of monthly changes, high salinity appears in January-April, with a highest of 27.5 psu in March, while the low salinity in May-August, with a lowest of 22psu in August, ; The season from Sept-Dec is the period of salinity rising; (4) According to the salinity distribution patterns and their relation with topography, climate and sea currents, 22 points for reference are selected. The lowest reference points of monthly salinity mostly occur in the northwestern Pacific Ocean; Highest amplitude is observed at D1 near the Yangtze River estuary and D2 in the south of Hangzhou Bay. However, the monthly correlation curves at D1 and D2 are obviously opposite, probably caused by the northward shifting of dilute water of the Yangtze River in summer, when the southward flow of the north Jiangsu coast current is inhibited by the Taiwan warm current, which is strong in summer and weak in winter.