The effects of carbon monoxide on the adsorption and desorption of nitric oxide on the surface of polycrystalline platinum foil have been studied using the technique of thermal desorption spectroscopy （TDS） under ultra-high vacuum conditions. It is suggested that the surface of polycrystalline platinum used in this study consists of Pt(111) plane, Pt(100) plane, and a small amount of high index surfaces. The -CO preadsorbed at 300 K prevents indirectly nitric oxide from adsorbing on the sites of the surface giving -No peak. The repulsive force between -CO and -NO is very strong, but a small amount of -NO adsorbs even on the surface of platinum saturated by 50 L CO. The adsorption sites for -CO coincide with those for -NO, and predosing with more than 10 L CO blocks entirely the adsorption sites for -NO. -NO reacts readily with CO producing carbon dioxide and molecular nitrogen, and the reaction between CO and NO proceeds via Langmuir-Hinshelwood mechanism.