water quality evaluation;  gray system;  whitening function;  clustering;  Environmental quality

The gray clustering decision is to generate a gray clustering matrix by analyzing and calculating the collected scattered information through the whitening function and the gray clustering weight, so as to classify the research objects. On the basis of discussing the principle of gray clustering method, taking the water quality assessment of a city as an example, the application of gray clustering decision in water quality assessment is discussed, and the water quality assessment procedure is compiled in VB language. This method and its software can evaluate the water quality of different water bodies, and the evaluation results objectively reflect the water quality status and category of water bodies, which overcomes the defect that single-factor evaluation is easily affected by individual factors.