Planning and selecting appropriate locating cage culture areas are essential for improving economic benefits and promoting the sustainable development of cage culture industry. However, several factors affecting cage culture including marine environment, production management and facility safety, which makes it a complex and multifactor decision-making process. Thus, developing an index system to evaluate the impact on the location of offshore cage culture is important. This paper employs the analytic hierarchy process (AHP) to construct an index system model for offshore cage culture site selection. The model includes three criteria layers and fourteen index layers, and we quantitatively analyzed the relative importance of each criteria layer and index layer based on expert judgment. Natural factors were the most important indicators in the criteria layer, followed by restrictive factors and finally social factors. Among the fourteen secondary indicators, water quality was the most significant, while food supply was the least. The AHP-based evaluation index system for offshore cage culture site selection can assess the importance of various factors accurately. The findings are beneficial for arranging offshore cage culture area appropriately, selecting regions suitable for offshore cage culture, and providing guidelines for optimizing and revising marine functional zoning.