Abstract: Combined the physical,chemical and biological index,using the Margelef multiple index and trophic state of comprehensive index(TSCI),the qualitative analysis and investigation of the water body quality of the subsidence pool are carried on in Huainan mining area,the inherent laws of water quality variation are discussed.As results the study discovered that this water body is affected seriously by organic pollution,and the content of BOD₅,COD_Cr,TP and some other indexes are higher,the water quality condition is tended to the eutrophication,where the relevance between the content of the nitrogen and the water quality change is more obvious than the phosphorus,moreover,the phosphorus is influenced obviously by the environmental factors.The Margelef multiple index also reduced from 3.20(1986) to 2.21(2005)(<2.5),and TSCI is 65.18,the water quality grade is mid-eutrophication(Ⅳ).It is suggested that,on the one hand, the change of the water quality of the subsidence pool in mining area is disturbed seriously by the environmental factors,on the other hand,also has its intrinsic law of development,and compared with the interior lake,it has the obvious particularity.