In this study, 7 main farmland drainage canals were evaluated by selecting 8 water quality indictors in Yanqi Basin from the year 2005 to 2013. Furthermore, the major pollutants were trackeded by Principle Component Analysis(PCA). Study results showed that the water quality in the said 7 canals was basically classified as Ⅴ grade, mainly characterized by brackish water or saline water. The major pollutants of water body in the agricultural drainage cannals firstly consisted of total nitrogen and ammonia; secondly, of the Chemical Oxygen Demand(COD_Mn)and Biological Oxygen Demand(BOD); and thirdly, of the total dissolved solids(TDS).