The invention relates to a linear internal combustion engine-based mixed energy conversion device, in particular to a gas energy storage device and power generating device integrated mixed energy conversion device, and belongs to the technical field of thermal energy and power engineering. The device consists of a linear internal combustion engine, a spark plug, a gas energy accumulator, a linear generator, a linear motor, an energy accumulation battery and an air inlet duct fuel injector; and the working process of the device comprises a starting process and an operating process of a cooling machine. The device has a simple structure, low machining cost, high reliability and high total energy conversion efficiency; by the device, chemical energy of an internal combustion engine fuel can be directly converted into energy and electric energy of compressed gas, the internal combustion engine can be pressurized by compressed gas energy in the gas energy accumulator, and the problems of insufficient oil combustion, high emission pollution and the like are solved; and the mixed energy output of the device is particularly suitable for various application occasions.