This paper proposes the flying capacitor(FC) initial charging method of the multilevel FC converter by using simple RC circuit. In the proposed initial charging circuit, the energy for charging FC is delivered from DC-side DC power supply during the start-up of the FC converter. The initial charging circuit works separately from the main FC converter and dose not disturb the main FC converter operation. The voltage stress of the main converter switches is limited the allowable level during initial charging operation. The effectiveness of the proposed FC initial charging method is verified by carrying on the PSIM simulation.