From the perspective of engineering practice, a new Cadence system modeling method is proposed considering the limitations of the Direct Current to Direct Current(DC-DC) system modeling methods in circuit application. A peak current-mode controlled DC-DC Pulse Width Modulation(PWM) buck converter system model is presented, which adopts ideal components in the Cadence platform to build model. A new circuit system is achieved by replacing the ideal system model with circuit construction in MXIC standard 0.5 μm BCD process in order to verify the performance of the model. Compared with the circuit system, the buck DC-DC converter chip based on the system model has a wide output voltage range and a large load current of 2 A at 340 kHz operating frequency.