Abstract: Due to the closed structure, it is difficult for valve reactor to dissipate heat from the core efficiently. In order to acquire the heat dissipation characteristics, and to predict the temperature during operation, the heat dissipation process needs to be accurately modeled. Consequently we first analyzed the structure and heat dissipation process, then established and simplified the heat dissipation balance equation of the core, which contains the key equivalent thermal resistance parameters. By studying the equation, we proposed a method for obtaining the equivalent thermal resistance parameters through parameter fitting by using multiple test data under different working conditions. To verify the method, a finite element calculation tool was used to simulate the reactor heat dissipation process. Finally, a reactor temperature rise test platform was designed and built, and multiple sets of test data were adopted to fit the equivalent thermal resistance parameters in the model. The simulation and test data reveal that the fitted results are accurate and the deviation of estimated core temperature is negligible, which shows a certain guiding significance for the structure design of the reactor.