In order to construct marine ranching in Zhoushan effectively, after analyzing the factors affecting the site selection of marine ranching, using AHP method to build up the evaluation model, we set up judgment matrix by delphi method, using Yaahp 5.3R1 software to evaluate the judgment matrix, and checked the consistency of judgment matrix, at last, obtained the weight value of the different projects. The result showed that the preferential order of the four sites selection is Ma’an archipelago marine ranching(0.289 5), Dongji island marine ranching(0.276 6), Yang’an Maotou marine ranching(0.221 9), and East Daishan island marine ranching(0.212 0). Zhoushan City could give priority to funding and project to construct Ma’an archipelago marine ranching and Dongji island marine ranching.