The segmentation of flood season of Geheyan reservoir was researched by using the changing-point method. The calculated results obtained from this method are compared with those obtained by climatological analysis method, the statistic method of flood events and the fuzzy analysis method, respectively. Compared with the flood peaks in Jingjiang River section, the main flood season of Geheyan reservoir should be lagged by 20 days. So the flood season of Geheyan reservoir may be divided into three sub-seasons, i.e., the early flood season from May 1 to June 20, the main flood season from June 21 to July 31, and the late flood season from August 1 to September 30.