According to the design parameters of air core reactor with equal high and heat flow, a three-dimensional fluid field-temperature field coupling simulation model is established, and the detailed temperature field and flow field distribution characteristics of reactor are obtained.The simulation results show that the temperature rise of each encapsulated coil in reactor is basically the same. The heat dissipation characteristics between the coil and the air duct are obtained by extracting the temperature and velocity distributions along the axial direction of the encapsulated coil and the air duct. On this basis, the internal encapsulated coil-air duct unit is selected to reflect the overall temperature rise of the reactor, combined with the experimental correlation of vertical pipe convection heat transfer, the reactor temperature rise calculation method is deduced. Based on the inductance conservation and structural equation of reactor, the linkage of the amount of reactor metal conductor with the overall shape proportion of encapsulated coil，air duct width and encapsulated number is constructed. The influences of all structural parameters on the amount of reactor metal conductor are also analyzed. Taking the amount of reactor metal conductor as the optimization objective, the optimal structural parameters of the coil are obtained by multi-island genetic algorithm.The optimization results show that the optimization method can significantly reduce the amount of metal conductor under the condition of ensuring the constant inductance and temperature rise of reactor and meeting the requirements of loss, which provides important guiding significance for the optimal design of reactor.