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In order to reduce the harm of dust and CO produced by tunnel blasting to the construction personnel, this paper puts forward an auxiliary ventilation method by adding the following portable gas exhaust device in the tunnel. In order to determine the effectiveness of the portable gas exhaust device, this paper simulated the application scene and application effect of the device based on the Numerical simulation software Fluent in Jiming Tunnel engineering, and obtained the tunnel flow field, dust and CO migration rule after the injection ventilation and the addition of the exhaust device. And the effect of the device on the flow field was verified, and the effect of the device on accelerating the discharge of dust and CO was verified. After the addition of the device, the change rule of CO concentration with time at five measuring points away from the palm surface was linearly fitted. The results show that: The addition of the following harmful gas exhaust device can effectively accelerate the discharge of dust and CO in the working area of the palm face. Within 120s of ventilation, the concentration of dust and CO in the same position after the addition of the device at the same time point is far lower than that under the pressure ventilation condition. After the addition of the device, the dust and CO concentration within 5m in front of the palm of 110-130s can be ventilated below the safe concentration. At the same time, the addition of the device will increase the disorder degree of the tunnel flow field to a certain extent. After the addition of the exhaust device, the change of CO concentration at the five measuring points in front of the palm of 30min of ventilation meets the single exponential function. Comparing the changes of dust and CO concentration before and after adding the portable harmful gas exhaust device, the effectiveness of the device was verified. [ABSTRACT FROM AUTHOR]