The invention discloses an environment heat absorption heat power conversion method. A working medium in a working medium source is leaded in a phase mixing heater, and then, is leaded in a combustion chamber for combustion; combusted gas is used for pushing an expansion acting machine for expansion acting; a fluid cooling medium is used for absorbing afterheat of the expansion acting mechanism and/or the combustion chamber; the fluid cooling medium heated by heat absorption is mixed with a fluid from the working medium source in the phase mixing heater for heat transfer; the fluid cooling medium enters the combustion chamber; or one part of the fluid cooling medium enters the combustion chamber, and the other part of the fluid cooling medium flows out from the phase mixing heater or by a separator, and is continuously used for absorbing the afterheat of the expansion acting mechanism and/or the combustion chamber after the environment absorbs environment heat. The environment heat absorption heat power conversion method can provide a heat power system with simpler structure and capable of effectively using the afterheat of an engine.