Based on the monthly water quality monitoring data and hydro-meteorological data from 2003 to 2012,this study analyzed water quality and nutritional status in Xin' anjiang reservoir and investigated the relationship between water quality change and hydro-meteorological factors. The results showed that the interannual variability of total phosphorus,total nitrogen,BOD and pH value were significant in the past 10 years in Xin' anjiang Reservoir. Chlorophyll a concentration increased in recent 10 years. Comprehensive nutrition state index showed that the reservoir trophic status was improved gradually from oligotrophic to mesotrophic. Nutrient and chlorophyll a was higher in riverine zone than transitional and lacustrine zone and in flooding season than dry season,which indicated that reservoir nutrients came mainly from non-point source pollution. The mean annual air temperature and water temperature decreased,while rainfall,out flow and in flow increased. The correlation analysis showed that hydro-meteorological factors had significant impacts on water quality index.