To measure COx, NOx, THC and other gas components of vehicle high temperature exhaust accurately, based on the principle of cyclone, the high temperature exhaust pretreatment regimen is discussed in detail. An improved cyclone and vehicular high temperature exhaust pretreatment gas circuit are designed, taking particulate filter chamber, cyclones, fluid resistance and membrane dryers as the main device. Particulate filter chamber is used to remove dust, metal spiral is used to drop temperature, cyclone is used to remove water and dust, resistance dispenser is used to remove water and membrane dryer is used to remove water. Without changing the exhaust gas composition and content, the gas clarity is improved. Experimental results show that the relative humidity of pretreatment gas is less than 2.5%, temperature is below 40℃, particles diameter is less than 5 μm and the content is extremely low. The sampling pretreatment system meets requirements of motor vehicle exhaust composition analysis module.