Abstract: The inductance of the coil with the core and without the core was measured by AC voltammetry keeping the same distance of the coil, the transformation of the inductance of the coil in the different connection modes was studied, and the influence of the core on the inductance was analyzed. The results showed that the inductance of general circuit was different in different connection modes, the connection mode of four coils connecting in series opposing was most suitable; the influence of the core on the mutual inductance was decisive, the inductance was different under different electric current.