The water quality assessment of Xingzi, Duchang and Tangyin stations in Poyang Lake has been evaluated by using the fuzzy comprehensive evaluation method. The three evaluation factors as ammonia nitrogen, permanganate and totoal phosphorus were selected for the evaluating indicators. The paper also set up the assessing matrix, calculated the weights of factors and obtained the characteristics index and finally evaluated the grades of water quality. This method can achieved objectivity and comprehensiveness that other methods can’t. Water quality monitoring data and evaluation results showed that water quality of three stations in Poyang Lake was still good from 2003to 2008. Most of time the water qualtiy was in class Ⅱ, Ⅲ level, but there were excessive in part times. In the case of worse than class Ⅱ, the water quality of three stations was worse during the dry water period than the rich water period and average water period.