Resonant Switched-Capacitor Converter (RSCC) is a promising DC/DC topology due to its high efficiency, high power density and wide output voltage range. This paper proposes a variable-frequency asymmetric control strategy for a four-switches RSCC, which simultaneously adjusts switching frequency and duty cycle of each switching-leg independently. By leveraging the asymmetric waveform of the resonant current, the proposed control strategy enables all MOSFETs to turn on with zero-voltage switching (ZVS) and three MOSFETs to turn off at minimal current. To achieve better performance, a variable turn-off current strategy is further proposed, enabling wider output power range, lower peak current value and reduced switching frequency variation range. A 400 W high power density prototype was built and tested, which has recorded 99% peak efficiency at (−48 Vdc to 48 Vdc) case.