The invention discloses an air intake mechanism of a non-supercharged gas engine, comprising a gas intake valve, a gas pipeline, an air filter, a Venturi mixer, a mixer pipeline, a disc valve assembly and a reciprocating swing structure, and the Venturi mixer Including the first input port, the second input port and the output port, one end of the gas pipeline is connected to the gas inlet valve, the other end of the gas pipeline is connected to the first input port, the air filter is connected to the second input port, and the disc valve The assembly includes a disc valve body and a disc valve, the output port, the mixer pipeline and the disc valve body are connected in sequence, the disc valve body is connected with the intake pipe of a non-pressurized gas engine, and the reciprocating swing structure drives the disc valve to rotate. The air intake mechanism of the non-supercharged gas engine provided by the present invention can accurately control the intake air volume of the gas engine, so that the non-supercharged gas engine can respond to the speed regulation feedback of the governor smoothly, quickly and accurately, so that the governor can fully exert its Its speed regulation performance can avoid the speed and flameout of the gas engine caused by the imbalance between the output and the load, and improve the production efficiency.