The invention provides an efficient air intake mechanism of an engine. The efficient air intake mechanism of the engine comprises a cam, a piston sleeve, a piston, a cylinder cover and a valve; a piston cavity is defined among the inner wall of the piston sleeve, the bottom of the piston and the top end of the cylinder cover; a roller is installed at the top end of the piston; a circle of inverted-T-shaped guide groove is formed in the cam in the rotating direction; the roller is matched with the guide groove, and the outline of the cam is matched with the piston; and a channel is arranged ina valve rod, one end of the channel communicates with the piston cavity, and the other end of the valve rod communicates with an air intake channel. According to the efficient air intake mechanism ofthe engine, a traditional valve spring is omitted, additional boosting is conducted in the ascending and descending processes of the valve, the air intake energy is stored when the valve is closed, the fullness coefficient of the cam can be increased, the pumping loss can be reduced, and thus the engine inflation efficiency is effectively improved. Besides, the efficient air intake mechanism of the engine is simple and compact in structure and beneficial for engineering application.