The invention relates to a process and device for heating gas by using a heat accumulation type heating furnace. The process and the device are characterized in that the heat accumulation type heating furnace is used for heating gas, the heated high-temperature gas is mixed with low-temperature gas in a mixing chamber to supply constant-temperature gas to a user; safety anti-explosion measures are provided; and accumulated coal in the heating furnace can be removed effectively. According to the invention, a method of inputting surplus air and mixing smoke is used to lower the temperature of a combustion chamber and the oxygen concentration of smoke and reduce the generation of accumulated coal. The process and the device have the beneficial effects that heat generated by combustion of gas in the heat accumulation type heating furnace is transferred to a heat accumulator and low-temperature gas exchanges heat with the heated heat accumulator to become high-temperature gas, and therefore constant-temperature gas can be provided for a process for extracting petroleum from oil shale in the petrochemical industry and other users.