A hybrid gas inflator utilizes a combustion chamber to generate a gas of hot jet. The gas pushes a piston downward and flows through a hole of the piston along its axis so as to break a pressure-resisting disc. The gas is then injected into a high-pressure gas container to heat up another gas therein. The hybrid gas gets expanded and is ejected through a plurality of exhaust outlets. This hybrid gas inflator can produce larger gas volume and therefore can reduce the size and weight of an inflator. Further, the impurities in the hybrid gas are congealed fast after two stages of pressure drop and can be removed easily by a filter.