Abstract: In order to research the differences of degradation effect on coke between potassium and sodium gaseous adsorption experiments on coke in potassium and sodium atmospheres were carried out, and the coke samples were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and thermal properties test. It is found that sodium more easily covers the surface of coke in surface-absorbed form, so the absorption amount of sodium is greater than that of potassium in the alkali atmospheres with the same mass ratio. Alkali metals absorbed on the surface of micropores have resistant effect on the solution loss reaction of coke. Compared with sodium in sodium-adsorbed coke, in the same absorption amount condition, more potassium in potassium-absorbed coke chemically combines with carbon and thus potassium-absorbed coke has a higher reactivity. In addition, potassium has strong destroying effect on coke. Potassium atoms can intercalate into carbon layers and cause the multidimensional expansion of microcrystals, which leads to breakages in the microstructure of coke. These new cracks result in the different ways of solution loss between potassium-adsorbed coke and sodium-adsorbed coke.