Abstract:This article retrieved PWV series of 5 stations in 2009 at Yancheng by GPS technology, and analyzed the variation characteristics with time of GPS PWV and its relationship to precipitation. The results showed that PWV of the summer achieved 43.15% of the annual amount, spring and autumn is respectively 19.21% and 26.43%, while winter is 11.21%. The minimum value of PWV appeared at 07:00—08:00 and the maximum at 16:00—18:00 during the daily variation. Daily amplitude is nearly 12mm in summer, about 7mm in spring and autumn, while in winter it is less than 5mm. PWV changes with 15 d, 30 d, 60 d, and semiannual multi-scale cycle. Moreover, the time domain is unevenly distributed and local variations are obvious. Summer precipitation occurs in 1-2 h after the peak of PWV appears;spring and autumn precipitation occurs in 2-3 h,while winter precipitation occurs more than 3 h. When the 2h increment of PWV reaches 5 mm, 6 mm, 5 mm, 4 mm in spring, summer, autumn and winter respectively, rainfall occurs with the probability about 60%-70%.