To study the influence mechanism of oxygen-containing functional groups on the surface potential of coal, the Zeta potential of three kinds of demineralized coal with different oxygen-containing functional groups was measured. Combined with molecular dynamics simulation and density functional theory calculation, the charging mechanism of coal surface was revealed. Studies have shown that the surface potential of coal is related to the number of oxygen-containing functional groups on its surface. The more abundant the oxygen-containing functional groups on the surface of coal, the more negative the surface potential. The surface charge of coal is the result of OH-preferential adsorption. OH-promotes the dissociation of O-H structure in carboxyl and hydroxyl groups on the surface of coal, so that the surface of coal is finally negatively charged. With the increase of coal metamorphism, the content of -COOH group and -OH group in coal shows a downward trend. Therefore, the absolute value of potential of long flame coal, coking coal and anthracite also decreases in turn, which eventually leads to the difference of electrostatic force between particles and bubbles