Changing trends of various rainfall series during 1951-2011 in the Taihu Basin were investigated.No statistically significant trends for the annual and flood season rainfall both for the whole basin and ninety-two gauges were tested.However, the rainfall time distribution within the flood season had significantly changed.The details are as follows: the monthly rainfall in May and September has a significant downward trend and the ratio of the rainfall in these two months to the total in the flood season declines while the ratio of the rainfall in June to August to the flood season total increases.This finding reflects a centralized tendency of precipitation temporal distribution in the flood season and has potential influence on water resources management and flood control of the study area.However, the cause remains to be further interpreted both from the aspect of global climate change and urbanization.