The invention discloses a method for determining the physical oxygen sorption amount of functional groups on a coal surface, and the method is applicable to researches on the spontaneous combustion characteristics of coals and the nature determination and classification of spontaneous combustion tendency of coal beds in coal mines. Through testing the content of main oxygen-sorbed functional groups on the surface of a coal sample and the variations of the main oxygen-sorbed functional groups after oxygen sorption and oxygen desorption, the physical oxygen sorption amount of the coal sample isjudged; and then, the oxygen sorption capability of each main oxygen-sorbed functional group is given quantitatively. The more the number of the main oxygen-sorbed functional groups on the surface ofthe coal sample, the bigger the variations of the main oxygen-sorbed functional groups after oxygen sorption and oxygen desorption are, and the larger the corresponding oxygen sorption amount is. Themethod can be used for effectively assisting in judging the spontaneous combustion tendency of coal beds in coal mines, and revealing the oxygen sorption capability of the coal sample from a perspective of the chemical structure of the coal sample. The whole determining process is implemented just by testing an infrared spectrogram of functional groups after oxygen sorption on the coal surface and an infrared spectrogram of functional groups after oxygen desorption through feeding nitrogen on the coal surface, so that the whole determining process is generally completed in 7-10 minutes, and the repeatability is quite high. The method disclosed by the invention is simple, easy to operate, time-saving, labor-saving, and accurate in test results.