Data of the Bayinbuluke weather station and the Dashankou hydrological station along Kaidu river in 1958 - 2007 and methods of Mann - Whitney Coefficient and Mann - Whitney were used to analyzed the runoff change and the impact of the precipitation and mean annual temperature change on the runoff. The study results showed that: (1) In the past 50 years,the inter - annual variation of the Kaidu river upstream flow showed a growth trend,experienced three significant leaps fluctuations,but the coefficient of variation was small,so the flow was relatively stable; annual runoff was mainly concentrated in the flood season,the most significant increase was in the winter,the rain and snow melt water which was supplied to the flow was relatively reduced. (2) Precipitation was the most important factor affecting the flow of Kaidu River; positive correlation between summer precipitation and summer traffic was very significant. Increased runoff in summer finally decided the increasing of annual runoff. (3) Temperature rise in the Kaidu river basin caused the increase of the ice and snow melting,which resulted in the non - flood flow increase,showed significant growth especially in the fall.