Taking the monthly monitoring data of surface river water quality in Xi'an from 2009 to 2017 as the research object, the comprehensive analysis of water quality is carried out by using multivariate statistical method, the main pollutants in water and their changing trend are explored by factor analysis method, and the sources of pollutants are analyzed. Comprehensive evaluation of water quality at each sampling point is made by principal component analysis. The results show that 24 water quality indicators can be described by 4 to 6 principal components from 2009 to 2017, and the cumulative contribution rate of variance is over 78%. The most influential indexes of Xi'an river water quality are organic matter and ammonia nitrogen. According to the factor load of the main control indicators, it can be seen that the overall water quality tends to be stable from 2009 to 2012, and the pollution intensifies from 2013 to 2015, but there are different degrees of mitigation in 2016 and 2017. In terms of the geographical location of the sampling points, Zaohe River is the most polluted, while the water quality of Heihe River is good as a whole.