Abstract The purpose of this paper is to realize the sustainable development of Three Forks Lake and control pollution. It analyzes the water quality of Three Forks Lake in the following aspects: PH, NH3-N, total phosphorus, total nitrogen, permanganate index, transparency, TDS, DO, conductivity. The author did some researches on water environment of Three Forks Lake by means of Cluster analysis and Inverse Distance-weighted Interpolation. The study reveals that most water area of Three Forks Lake is polluted seriously because the water here is having a PH greater than 7 and a greater turbidity, and the water nearer to inland is harder, having more nitrogen, higher permanganate index, less dissolved oxygen. This paper not only theoretically studiess the water quality of Three Forks Lake by cluster analysis, but also get a conclusion of pollution with the combination of the information from Figure 1, Figure 3 and Figure 4, which bascially identical with the authority's data.