Abstract: in order to study the carbon monoxide adsorption/desorption features of the medium and low rank coal,four samples from Cuijiazhai lignite ,Jinggezhuang gas coal Linnancang fat coal and Wangnian coking coal were collected and the coal qualiy analysis the isothermal adsorpton/desorption tests of carbon monoxide and the infrared spectrum analysis before and after the adsorptiore samples. The results showed that the carbon monoxide adsorption capacity of the four samples were in the following order,Linancang fat coalwould be the highest.Jinggezhuang gas coal and Wannian coking cal would be the second and Cauijizhailignite would be the lowest.The adsorptionldesorption process was irreversible and a hysteresis would be existed in the desorption process. Due to the different rank of the coal,the major control factor of the carbon monoxide adsorption would be different.From the stage of the lignite to gas coal ,the equilibrium moisture contentin the coal would have a high infuence.From the stage of gas cal to fat coal,the moisture content of the coal and the macerals played aleadingrole.From the fat coal to coking coal stage,the oxygen functional group in the coal and the variation of the macerals would make a high contrbuton to the carbon monoxide adsorption. The study held that the moisture content of the medium and low rank coal and the variation of the oxygenfunctional group in the molecular structure would be the major causes to make the difference of adsorptionldesorption law of carbon monoxide.