The invention provides an engine adopting a self-adaptive machine case and a self-adaptive fan. The engine comprises the self-adaptive machine case, the self-adaptive fan and a fuel gas generator; theself-adaptive machine case comprises a self-adaptive machine case driving execution part, an inlet section self-adaptive machine case, a fan section self-adaptive machine case, an engine middle section self-adaptive machine case and an outlet section self-adaptive machine case, wherein the inlet section self-adaptive machine case, the fan section self-adaptive machine case, the engine middle section self-adaptive machine case and the outlet section self-adaptive machine case are sequentially connected; the self-adaptive fan comprises self-adaptive fan blades and a fan driving execution part;a self-adaptive external duct is formed between the engine middle section self-adaptive machine case and an internal duct machine case of the fuel gas generator; an internal duct is formed in the internal duct machine case; the self-adaptive machine case driving execution part drives the self-adaptive machine case to move to control the cross section area of the external duct; and the fan drivingexecution part drives the self-adaptive fan blades to move in the axial direction to enable the self-adaptive fan blades to be matched with the fan section self-adaptive machine case.