Water pollution is one of the most serious environmental problems in China

and its control has become the urgent task for our environmental conservationists.In order to improve the ecological environment of the northwest of China

it is of great importance to study and protect the lakes in the area.The Sand Lake of Ningxia Hui Autonomous Region was chosen as the study object and principal component analysis and fuzzy comprehensive evaluation method were applied to evaluate its water quality variations from 2000to 2009.We found that the water quality was getting better during the study period.Specifically

the fuzzy comprehensive evaluation method illustrated well the water pollution levels and principal component analysis adequately detected the water pollution degrees.The results were more objective with combination of principal component analysis and fuzzy comprehensive evaluation.