Abstract: Objective & Methods To study the effect of collectors with different molecular structures on the flotation of oxidized coal, n-dodecane, isododecane and cyclododecane, which have the same number of carbon atoms but different structures, were selected as flotation collectors to explore the flotation effect of coal samples from Huaibei. Result The flotation results showed that n - dodecane and isododecane had good collector performance when the amount of collector was in the range of 0.9～1.2 kg/t. In the same interval, the isododecane and cyclododecane have good selectivity. When the dosage of isododecane is 1 kg/t, the ash content of flotation cleaned coal is as low as 11.37%. FTIR test, XPS test, contact angle test and wetting heat test were carried out on coal samples before and after the action of chemical agents, to explore the mechanism of chemical agents improving the flotation effect of coal samples. The results show that the oxygen-containing groups on the surface of the coal sample deteriorate the floatability of slime. Conclusion Three kinds of chemical agents with differentmolecular structure can improve the floation property of coal samples in different degrees, among which the relative content of C-C/C-H of coal samples treated with isododecane is significantly increased, the content of hydrophilic groups such as C-O, C=O, O=C-O is significantly decreased, the contact angle is 23.90° higher than that of raw coal, and the heat of wetting is 1.041 J/g higher than that of raw coal. It shows that isododecane can effectively cover the oxygen-containing groups on the surface of oxidized coal, increase the area of the hydrophobic region, hinder the formation of hydration film on the surface of coal particles, make the agent itself spread better on the surface of coal particles, and enhance the adsorption firmness, thus strengthening the flotation effect.