The invention provides a combined air valve of a high-speed diesel engine. The combined air valve of the high-speed diesel engine comprises a cam, a first air valve and a second air valve, wherein a first guide slot and a second guide slot are separately formed in the upper circumference of an outer contour wall; the upper end of the first air valve is connected to a first roller slidably matchedwith the first guide slot and the lower end of the first air valve corresponds to a pit of a piston; and the upper end of the second air valve is connected to a second roller slidably matched with thesecond guide slot and the lower end of the second air valve corresponds to the top of the piston. By cancelling a conventional air valve spring, the contact stress between the cam and the air valvescan be reduced effectively, the acceleration of the cam is improved, and the fullness coefficient of the cam is increased; a relatively high charging efficiency can be acquired in a high speed workingcondition while the air pit is cancelled, so that the high speed performance of the engine is improved effectively. The combined air valve is simple and compact in structure, and engineering application is facilitated.