This disclosure investigates and evaluates coupled inductor in interleaved multiphase three-level DC-DC converters. If non-coupled inductor is used and maintaining the inductance of inductor, multiphase three-level DC-DC converters interleaving operation will increase the inductor current ripple, although the overall current ripple and Common Mode voltage will be smaller. To reduce the inductor current ripple, inverse coupled inductor is employed to reduce the size of inductor. The benefits of coupled inductor are analyzed and the analysis results are verified by simulations. By adding coupled inductor and interleaving, it is possible to achieve smaller inductor current ripple, smaller input and output capacitors as well as smaller CM filter simultaneously. In addition, novel integrated structures are proposed for small size, weight and cost. The proposed structure can reduce the volume by 40%, compared with conventional non-coupled inductors used in non-interleaved three-level DC-DC converters.