To determine the optimal insulation thickness and heat transfer coefficient of FRP fishing vessels, this paper established the mathematical model of heat transfer of the FRP fishing vessel structure. Based on the theoretical analysis model. The influence of the insulation thicknesses on the heat transfer coefficients and frozen loads of FRP fishing vessels with different ship sizes are analyzed under different design temperatures. The results indicate that: the maximum heat transfer coefficient of an FRP fishing vessel is smaller than 0.15 W/m2·K, which is much smaller than that of a steel vessel; Most of the FRP fishing vessels with a length of 30-40m are ultra-low temperature or ordinary cold fishing vessels. The thickness of the insulation layer has little effect on the selection of refrigeration equipment. The thickness of the insulation layer can be determined according to the minimum requirement of the actual structure calculated. The value of the heat transfer coefficient is 0.1 W/m2·K; Most of the FRP fishing vessels with a length of 20-30 m are ice-fresh fishing vessels, and the influence of the insulation thickness on the production cost is much more than the freezing cost. The thickness of the insulation layer can be determined according to the minimum requirement of the actual structure calculated. The value of the heat transfer coefficient is 0.15 W/m2·K. This study provides a theoretical basis for the refrigeration system design of FRP fishing vessels in the future.