A three-dimensional fluid-temperature field simulation model is established in this paper based on the design parameters of the air core reactor. The detailed temperature field of the reactor with and without the rain cover and sound arrester are obtained, and the heat dissipation characteristics of reactor are achieved by analyzing the temperature of coils and flow velocity of fluid. According to the change of fluid velocity, the reason for the significant increase in the temperature rise of the reactor under the rain cover and sound arrester can be obtained. In order to reduce the temperature rise of the reactor, the structural parameters of the rain cover and sound arrester, which affect the temperature rise of the reactor, is selected. Combined with the Latin square experimental design and finite element simulation method, the temperature field simulation results with different structural parameters are given. On this basis, the Kriging approximate model is constructed, which build the correlation between the maximum temperature of the reactor and the structural parameters of the rain cover and sound arrester. Meanwhile, the influence degree of the structural parameters on the highest temperature of the reactor is achieved by sensitivity analysis technology. The best structural parameters of the rain cover and sound arrester are obtained based on the particle swarm optimization algorithm. The optimization results show that the maximum temperature rise of the reactor drops dramatically from 73.6 ℃ to 61.2 ℃ under the best structural parameters. Thus, the optimization method has an important guiding significance in improving the heat dissipation capacity of the reactor.