A cascade power-factor-correction (PFC) converter is a nonlinear system cascaded by a PFC converter and a direct current-direct current (DC-DC) converter. According to the nonlinear model of the cascade PFC converter derived, we simulate the interstage coupling nonlinear dynamical behaviors of the system, and the simulation results are verified experimentally. The results shows that with the decrease of the PFC output capacitance the bifurcation may appear, which results in the change of the DC-DC output voltage. Likewise, the dynamical behavior of the PFC stage may change with DC-DC load resistance. When the duty ratio of the DC-DC stage becomes saturated, the coupling process between the PFC stage and the DC-DC stage is very complicated.