This paper proposes a general methodology to analyze the interleaved pulse width modulation (PWM) dc-dc converter. A unified and simple model is constructed and the complete electrical behaviors of the interleaved PWM dc-dc converter could be predicted. Features of the interleaved PWM dc-dc converter are investigated based on this model. Insightful conclusions are derived and can be used to guide designs. This model could serve as a solid foundation for further research, and it is valid to all the common interleaved PWM dc-dc topologies. As an example of its applications, the input current of the interleaved boost converter is investigated in detail. Simulation and experimental results have successfully validated against theoretical analysis.