The invention provides an automatic multi-cylinder hot air engine and a use method of the automatic multi-cylinder hot air engine. The automatic multi-cylinder hot air engine comprises a main device body, a power output device arranged in the main device body, an auxiliary power device arranged in the main device body and a turbocharging device arranged in the main device body, wherein the power output device comprises a first steam cylinder arranged in the main device body, and a first combustion chamber with a downward opening is arranged in the first steam cylinder. The hot air engine focuses on high temperature waste heat produced by fuel combustion, the waste heat is absorbed and utilized to heat the water in a heat recovery chamber to boil the water so as to generate air motion, andthen the turbocharging effect is realized through transmission. The fuel is combusted more sufficiently, so energy resources can be saved. Furthermore, a turbocharging device is arranged in the engine, has small space occupancy and is light.