Abstract: Aiming at the problems such as complex system, large maintenance and measurement delay in the pretreatment of gas on-line monitoring in industrial process, the in-situ permeation tube pretreatment device is developed based on the physical characteristics of microporous ceramics and aerodynamics principle. The pretreatment device mainly includes two laser emitters and a permeation tube cavity. When the gas flows through the permeation tube, the pressure drop will be formed before and after the wall of the incoming direction, due to the action of flow around. Under the pressure drop, the gas will be filtered through the permeation tube and then enter the tube to be measured by laser. Firstly, the coupling field of pipe and permeation tube are simulated by CFD numerical simulation, and it is shown that under the condition of single variable, the gas renewal rate increases with the increase of flow rate and inner diameter, and decreases with the increase of outer diameter. Then the experimental device is set up for experimental verification, and the result is consistent with the flow field simulation. On this basis, the in-situ permeation tube pretreatment device is developed and applied in the field, and the portable analyzer is used for comparison which show the error between them is less than 2%. Compared with the existing pretreatment devices, the permeation tube cavity is installed in the pipe, the measurement environment is consistent with the working condition, and the sampling path is short, which can realize high fidelity and fast on-line monitoring of industrial process gas.