Using the snowmelt flooding disaster data from 1950 to 2006, snowmelt flooding characteristics of the Xinjiang region were analyzed. The results indicate that snowmelt flooding over Xinjiang region usually occurred in the northern slope of Tianshan Mountains, especially in the Ili River Valley and Tacheng area, while snowmelt flooding most easily occurred for the time from mid March to early April. On the basis of it, climate background, weather process, diagnostic analysis were analyzed on the possible weather causes for snowmelt flooding occurring in mid March 2009. Finally we can see the basic condition for snowmelt flooding occurrence that the rainfall in February 2009 was obviously more than the average value in the same period of the past years, and air temperature rapidly and continually increased after the cold air passing through, all these may be the most possible causes for the snowmelt flooding in mid March 2009. During the durative and rapid heating process, the time for mean temperature being higher than 0 ℃, the highest temperature being higher than 5 ℃ as well as warm advection center appearing has the instructive significance to snowmelt flooding forecasting.