Abstract: Hybrid DC circuit breaker is one of the most promising solutions to the problem of DC circuit breakers. In this paper, a natural commutation hybrid DC circuit breaker based on vaccum switch and gas switch in series is proposed. In principle, the natural commutation is driven by the high arc voltage of gas arc, and the transient recovery voltage caused by the turn-off of power electronics devices is withstood by the vacuum gap due to its fast dielectric recovery. The proposed breaker is characterized by the qualities of low loss, reliable breaking, small size and low cost. The characteristics of the arc voltage of gas mechanical switch are analyzed, and the laws of effects of different factors such as opening speed, magnetic field, gas type, arc current, and gas pressure on the arc voltage of gas mechanical switch are researched. The design method of gas and vaccum mechanical switch is presented. Based on this, a 10 kV natural commutation DCCB prototype is developed and tested, and the breaking current reaches 15kA, which effectively verifies the feasibility of the proposed hybrid switches scheme.