Water quality evaluation is of great significance in protecting the water environment. Dissolved oxygen (X1), Permanganate index (X2), BOD5 (X3), Ammonia nitrogen (X4), Total phosphorus (X5), and Fluoride (X6) are selected as the assessment index, and the game-gray target model is introduced. Then, the gray target water quality model in the Tao Jiang River section is established. The weight coefficients of each index are calculated using the game combination weighting method, and each sample’s synthetic target center distance is determined using the gray target model. Finally, the levels of water quality are determined. The suggested model can mine the small sample data to the greatest extent and weaken the information shortage problem caused by the small sample to a certain extent. The suggested model is feasible, has higher validity and accuracy in evaluating water quality, and has better practical application prospects. The final quality grade of water can be evaluated quantitatively. Therefore, it can provide a new approach and a new way to think about future water quality assessments.