Abstract: In order to get the trend of water quality change of Gehu Lake in Jiangsu Province in recent years and construct a new comprehensive water quality assessment model for the region, the inter-annual and annual variation trends of different water quality indicators were analyzed based on the long-term water quality data from 2008 to 2016. We issued 100 questionnaires and got the subjective weight based on the expert's experience and objective weight based on information entropy theory. According to the comprehensive weight, a new comprehensive water quality assessment model was built to assess the water quality in different zones of Gehu Lake. The result showed that: various water quality indicators in the 9 years all presented downward trend, especially a significant reduction after 2008, the possible reasons being the good management in recent years. The water quality indicators in buffer zone were generally higher than the rest of the lake and with 37.2% higher in maximum. The annual variation of different water quality indicators showed a trend of decreasing first and then increasing. The water quality was generally poorer from November to February. Based on the new model, the water quality of different zones was analyzed. The water in core zone and development and utilization control zone belonged to class Ⅲ and the water in buffer zone belonged to class Ⅳ. The measures were needed to be developed to improve the water quality. The analysis results are accordance with the observed data and the local practical condition, showing the model has scientific and practical value and can provide a scientific basis to assess the water quality of the region.