The invention provides a differential-pressure type gas valve lift adjusting mechanism and belongs to the technical field of mechanical design. The differential-pressure type gas valve lift adjusting mechanism comprises a gas compressor, an engine, a turbine, connecting pipes, a valve seat, a valve body, a rotary shaft, a containing cavity, a fixed body, penetrating pipes, an elastic component, a separating board, a rotary body and a connecting board. One end of the rotary body extends into the first penetrating pipe and makes sealing contact with the wall face of the first penetrating pipe, the other end of the rotary body is fixedly connected with the separating board, one end of the third connecting pipe is communicated with an engine gas inlet pipe, and the other end of the third connecting pipe penetrates through the outer wall face of the containing cavity and then is communicated with the containing cavity. When the pressure of the engine gas inlet pipe is high, the valve body is driven by the rotary body to rotate in the clockwise direction, the exhaust gas recirculation rate of the engine is high, and the detonation pressure of the engine is low; when the pressure of the engine gas inlet pipe is low, the valve body is driven by the rotary body to rotate in the anticlockwise direction, the exhaust gas recirculation rate of the engine is low, and the fuel consumption of the engine is low. The differential-pressure type gas valve lift adjusting mechanism is reasonable in design, simple in structure and suitable for an exhaust gas recirculation system of a supercharged engine.