From 2011to 2012, in order to find out water quality and sources of pollution of three rivers in Yingjing county, Sichuan Province, the paper monitored pH value、temperature (T) and concentration of dissolved oxygen (DO)、ammonia nitrogen (NH3) and total phosphorus (TP)、Chemical oxygen demand (COD) and Total nitrogen (TN) in different water periods and surveyed the lifestyles of the people living in the river basin. The results show that the above five indexes (pH、T、DO、NH3and TP) all reach class II of environmental quality standards for surface water. Other two indexes, COD and TN, are under the class II, and they are different in the three rivers. We also find that the two indexes are different in the three different periods (moderate period, flood period, low water period). Of the three periods, water quality in low water period is the worst , and it just reaches inferior class V. According to the Biological Diatom Index(BDI). The results show that the three rivers are seriously polluted and there are difference in the three rivers. The result from using BDI is consistent with the result from monitoring the water quality. The sources of pollution are from sewage in the river basin, the application of fertilizers and livestock cultivation. In order to improve the river situation, the education on environmental protection in the community should be strengthened, the processing capacity of garbage and polutant be enhanced, and the integrated river basin management be actively carried out.