The water pollution in Bosten Lake in Xinjiang over the last ten years was evaluated and analyzed using the principal component analysis and the system clustering method.Analysis shows that,during the period from 2000 to 2009,the score of comprehensive evaluation of water pollution in 2000 was the highest,indicating that the most serious water pollution over the last ten years occurred in this year.The score of comprehensive evaluation of water pollution in Bosten Lake over the last ten years has a declining trend,indicating a water pollution alleviation in the lake.Clustering analysis shows that the water pollution in the lake has not been alleviated,and the score of comprehensive evaluation of water pollution even had an increasing trend in 2005,which indicates that the water pollution in Bosten Lake was still serious and the water quality was unsatisfactory.