In the light, economical and compact development of offshore wind power platforms, annular hollow reactors have a broader development space. Due to the special structure of annular hollow reactors, the research methods of dry hollow reactors are no longer applicable. In this paper, the calculation principle of the inductance of the annular hollow reactor is supplemented by the energy method, and the principle of using the flux linkage method to calculate the inductance of the annular hollow reactor is proposed and expounded for the first time. Using Matlab to program energy method and flux linkage method, the inductance of annular hollow reactor with arbitrary parameters can be calculated. The results show that when the number of thread cakes is large, the energy method is more advantageous, and when the number of thread cakes is small, the flux linkage method is more suitable. Therefore, the two methods can be complementary to determine the inductance value of the annular hollow reactor. Based on the finite element simulation results, the optimization direction of energy method and flux linkage method is proposed.