The LC unit is an important component of the EMI filter for its easy "inductance-inductance" integration, and usually the ideal LC unit is composed of the double helix structure. Based on the different ways of connection on LC units, a new structure is presented, which is mainly used for the integration of common-mode inductors and differential-mode capacitor. According to the transmission line theory, the equivalent model of LC units is established, and then the parameter models of the new structure are analyzed under the conditions of the differential-mode current and the common-mode current. Moreover, the research shows that the proposed model has larger common-mode inductor, which is also confirmed by the corresponding experiment.