Based on physical features of the basin，the Dongliao river is divided into two parts，namely hill- river and plainiiver with the Erlongshan lake as the bound- The monthly and yearly evolution of water quality were studied by means of PCA，and its response to environment acidification is analyzed by means of correlation. The water is seriously polluted and must be renovated. The primary pollution factor is organic mat?ter. The pollution of lower reach must not be neglected. The evolution of water quality is monthly and yearly， and the response to the acidification of environment is strong.