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Using the rainfall data of 11 counties over the Nansi Lake basin from 1971 to 2007, analyzed are the starting and ending times of the first and the last heavy rainfall over the Nansi Lake basin, as well as the temporal and spatial distributional characteristics of heavy rainfall. It is found out that there are different temporal and spatial distributions in heavy rainfall over the Nansi Lake basin. The probability of daily maximum possible precipitation exhibited a 〖WTBX〗Λ〖WTBZ〗(x)typed progressive distribution. The daily maximum precipitation that happened once in certain years is estimated by using the Gumbel distribution. Estimation results show that the return periods of the estimated daily maximum precipitation of the next 10 years, 20 years, 40 years are basically the same as those in history, which is a good reference for the estimates of next 50 to 200 years.