Based on soft-switched continuous conduction mode boost converter, a zero-voltage zero-current switching DC/DC converter is proposed by introducing a flyback-unit and a voltage-double-unit. The proposed converter can achieve high voltage gain without operating at extreme high duty cycle. Moreover, by replacing the output diode of conventional boost converter with an active switch, zero-voltage-switched turn-on of switches and zero-current-switched turn-off of diodes can be achieved, which reduce switching loss and alleviate reverse-recovery problem of diodes. Furthermore, the energy in leakage inductor can be transferred into the output of the converter to improve the efficiency. The operating characteristics and the voltage gain of the proposed converter are analysed. Experimental results of a 100 W prototype are provided to verify the theoretical analysis results.