In recent years,the global warming trend is clear. Semi - arid region of western Jilin locates in the northwest of Jilin province and its fragile ecological environment poses a serious threat to sustainable regional economic growth and agricultural development. In order to provide agricultural production,water use,ecological protection and the policy with theoretical basis,the trend analysis,wavelet analysis,and Mann - Kendall test were used to analyze the characteristics of climate change by using the temperature and precipitation of 6 stations in this region during 1961 - 2010. The result shows that temperature displayed a ascendant tendency,with the value of 0. 37 ℃ /10a. The maximum ascendant tendency was in winter with 0. 62 ℃ /10a. The precipitation showed a descendant tendency,which was about 6. 75mm/10a,with particularly evident of 13. 79 mm/10a in summer. In different time scales,change trends of temperature and precipitation were different. The annual average temperature had about 5a,12a and more than 30a oscillation periods and a mutation in 1989,but the average annual precipitation had about 5a and 30a oscillation periods,with a frequently interannual alternating. On more than 30s time scales,temperature had experienced 3 large time scale changes,whereas precipitation had experienced 4 times. By analyzing the aridity index,it displayed an ascendant tendency generally,but the upward trend is not obvious,and the increase extent decreased gradually from west Baicheng to east Sanchahe. It shows that in recent 50s aridity index changes in semi - arid region of western Jilin fluctuated,which had about 6a,10a and 35a oscillation periods and mutated in 1989 - 2002.