The invention provides a six-stroke gasoline engine and a control method and device thereof. The control method includes: igniting at a first compression top dead center; in an observation window, detecting inner pressure of a cylinder through a cylinder pressure sensor; acquiring accumulative combustion heat release in the observation window according to the inner pressure of the cylinder; according to the accumulative combustion heat release, acquiring a first-stage combustion state of the six-stroke gasoline engine; according to the first-stage combustion state, adjusting parameters of the six-stroke gasoline engine so as to trigger second-stage HCCI combustion of the six-stroke gasoline engine. The six-stroke gasoline engine and the control method and device thereof have the advantages that combustion stability of the six-stroke gasoline engine can be improved, operating range of HCCI combustion mode can be widened, fuel economy is improved, a great amount of exhaust HC emission caused by a fire or incomplete combustion can be decreased, burden of a gasoline engine after-processing system is greatly decreased, implementation is simple, and precision is high.