A plunger lifting mechanism of a rotary-valve gas carburetor includes a carburetor body, a cam, a plunger, a torsion spring, a fixed plate, a throttle wire bracket, a main measuring needle, a sleeve and a main jet pipe. The plunger is rotatablely mounted in the carburetor body, which passes through the cam, the torsion spring and fixed plate in turn and then extends out of the carburetor body, and a top of the plunger is connected with the throttle wire bracket and then fixedly connected with the sleeve; the fixed plate is fixedly connected with the carburetor body; one end of the torsion spring is elastically suppressed by the fixed plate, and the other end of the torsion spring is elastically suppressed by protrusions on side walls of the plunger. The configuration can ensure sufficient flexibility of its plunger and improve the reliability of the carburetor.