The absorption and utilization of rainwater is the original intention of sponge city construction. Taking rainwater resources as the research object, a rainwater resource utilization potential evaluation system was set up based on rainwater resources conditions, the implementation degree of rainwater resources, regional ecological environment conditions, economic feasibility and comprehensive rainwater demand rate. The analysis method and fuzzy comprehensive evaluation method were used to evaluate the utilization potential of rainwater resources in sponge city construction. Taking the pilot zone of sponge city construction in Linhai City of Zhejiang Province as an example, the comprehensive runoff coefficient method can be used to calculate that the utilization of rainwater resources can increase by 28.46×104 m3 after the construction of sponge city. The utilization potential of rainwater resources in the region is assessed by using the evaluation system. The evaluation results show that the utilization potential of rainwater resources in this region is Grade I, and the utilization potential of rainwater resources is large, that is, rainwater resources are abundant and can be fully utilized. This is in good agreement with the results calculated by the integrated runoff coefficient method, indicating that the evaluation system has certain rationality. This provides a basic evaluation method and theoretical support for other areas where rain water utilization is carried out, and has certain engineering significance.