Abstract: Through analog devices, catalytic oxidation method is used to purify CO/air mixed gas in this paper. The purification performances of three kinds of catalysts, circulation velocity and time on CO/air mixed gas is researched in the ambient temperature and pressure. The experimental results show that three kinds of catalysts have a certain level capacity for purifying the CO/air mixed gas with low concentration and the purification performances have relationship with the kind of catalyst, circulation velocity and time. The ACO-2 shows better performance than the other two. Within a certain rage, the elevation of the circulation velocity attributes to the purification performance of catalyst. When CO concentration is in the rage of 400 ppm, the purification rate is slower and slower as time goes on.