In this paper, the slow-scale bifurcation phenomenon of the one-cycle-controlled three-level Boost power factor correction (PFC) converter is studied in depth, aiming at analyzing the influence of main circuit parameters on the stability of the system based on Floquet multiplier method. Firstly, the working principle of the circuit is analyzed, and a simplified model is derived according to the power balance principle. The periodic solutions are investigated using the harmonic balance method, and its stability is studied by the Floquet theory. By calculating the Floquet multiplier, the influence of the voltage compensator resistor Rvf on the slow-scale behavior of the system is analyzed. The simulation result verifies the correctness of the simplified model and theoratical analysis. Finally, the stability boundary composed of filter capacitor C and load resistor R as well as feedback resistor Rvf and capacitor Cvf is calculated and simulated under certain conditions. The circuit simulation result is consistent with the theoretical calculation. The results show that the correct choice of circuit parameters of three-level Boost PFC converter is very important for achieving its stable operation and improving the power factor.