For studying the actual problem about reservoir flood season division on the control basin influenced by high mountain glacier, and taking the Jiahezi Reservoir of Manas River basin as the object of study, the main influence factors of flood season division were discerned and regarded as the basis of division. In the qualitative and quantitative analyses, four kinds of methods such as cause analysis, vector statistics, fuzzy analysis and systematic cluster were synthesized and the applicability of them analyzed. Finally, in combination with the hydrometeorological characteristic of the north slope climatic zone of Tian Mountain and the operation of the reservoir, the flood season range are divided: 10 July 30 July flood season as main flood season and 1 August 15 August as later flood season. The result? offers a theoretical basis for the operation of Jiahezi Reservior by stages.