In this research the typical Tianshan mountain lakes - Bosten Lake and Issyk - Kul Lake were taken as the study objects,by using 1960 - 2015 hydrological data,climate data,and social - economic data,correlation analyze and principal component analysis were utilized to find out the driving factors. The results showed that: (1) Over the past 55 years,under the influence of human activities and climate change,Bosten Lake and Issyk - Kul Lake has experienced volatility change of increase and decrease process,among them Bosten lake was characterized with decline - rise and decline change trend. However Issyk - Kul lake was characterized with decline - rise - decline and rise change trend. (2) Principal component analysis results showed that the first principal component is the human factor for Bosten Lake water level change,the second principal component is the climatic factor. Instead,the first principal component is climatic factor for Issyk - Kul water level change, the second principal component is the human factors.