Taking karst areas of Chongqing as study case,this paper analyzed the climate changes on karst ecosystem in the aspects of hydrologic regimes and water resources.According to the hydrologic data and meteorologic data,the influence of temperature and precipitation on elements of water resources were studied with mathematic analysis method.The results show that precipitation change had a great influence on runoff,showing dramatic positive correlation.With precipitation decreasing,runoff descended.Furthermore,precipitation change resulted in droughts,floods and normal years occurred by turns,and durative time of droughts and floods was long.In the karst areas of Chongqing,air temperature is an important factor of affecting evaporation.Potential evaporation had seasonal change and annual change obviously with temperature change.With temperature ascending,evaporation increased,or else decreased.In space,evaporation in the west was higher than that in the east,evaporation in the north was higher than that in the south.