The assessment model of eutrophication has been established by used of Accelerating Genetic Algorithm and Logistic Curve in this paper. According to the model, the eutrophication levels of the different season from 1996 to 2003 in Wuliangsuhai Lake have been concluded. Based on the level, the season-year changes of the eutrophication main-control factors in Wuliangsuhai Lake have been analyzed. The result shows that all the main-control factors of eutrophication remain forth level and except that the total phosphorus has great fluctuation, the others are rising by and by from 1996 to 2003. The whole levels of the water quality have beyond the forth level and close to the fifth level.