In order to better understand the changing rules of flood-season runoff in the west Tianshan Mountain region, it is necessary to guide the rational development and efficient utilization of water resource and provide the basis for flood control and disaster mitigation there. Based on the floodseason runoff data, the evaporation data ,the precipitation data in 1960-2005, the runoff variation law of flood season is explored with the methods of center time（CT）, moving-T test, and moving-F test. The results showed that flow center time that floodseason runoff had a slight advance tendency from 1960 to 2005; The results of concentration period, concentration degree and variation range showed a decreasing trend from 1960 to 2005; The floodseason runoff showed an increasing trend from 1960 to 2005, and the abrupt change of floodseason runoff occurred in 1997; It was concluded that abrupt change of evaporation and precipitation occurred in 1997.Therefore, it was inferred that the increase of abrupt change of floodseason runoff in 1997 was due to the increase of precipitation and the decrease of evaporation after 1997.