Noise reduction device of exhaust pipe

The invention discloses a noise reduction device of an exhaust pipe. The noise reduction device of the exhaust pipe comprises a barrel. A noise reduction cavity is formed in the barrel. The two ends of the barrel are provided with an air inlet and an air outlet respectively. Two partition plates and two baffles are installed in the noise reduction cavity sequentially in the direction of the air outlet. A connection pipe penetrates through the upper portions of the two partition plates and penetrates through the lower portions of the two baffles. The lower portion of each partition plate is provided with a plurality of through holes. A plurality of air holes are formed in the upper portion of each baffle. A ventilation pipe is connected between the air outlet and the air inlet and penetrates through the partition plates and the baffles. A pneumatic control valve is arranged at the connecting position between the ventilation pipe and the air inlet. When the flow of air flowing in from the air inlet is small, noise generated by air flow correspondingly is low, the pneumatic control valve is closed directly, the air flow is directly exhausted from the ventilation pipe via the air outlet, the possibility of residual air flow in the noise reduction cavity is decreased, and the service life of the noise reduction device can be prolonged.