Abstract: In the phase-shift control scheme of three-level full-bridge converter, some switches can’t implement soft switching. In the chop plus phase-shift（CPS） control, the total harmonic distortion（THD） of the transformer primary side voltage is high. To resolve this issue, a new symmetrical double phase-shift（SDPS） control scheme was proposed. A comparative study was done between CPS and SDPS control.Through analysis of one switching cycle, we can see that all switches can implement soft switching in SDPS control.Fourier analysis of the voltage showed that THD of the transformer primary side voltage was low in SDPS control. By analyzing how the THD varied with chopping angle, the optimal steady state operating point of this control scheme was got in SDPS control. A three-level full-bridge device was made and the analysis was verified by experiments.