Abstract: The effect of the high density fine coal on coal flotation behavior at different pH values is studied by micro-flotation,particle size analysis and surface Zeta potential of coal particles. The result show that The flotation yield of the micro-flotation test under acidic condition is the lowest,and it has the highest yield in under neutral condition. The decrease of the pH value of the ore slurry will cause the dispersion of the particles to become worse,the agglomeration phenomenon between the particles is obvious, and the high density fine coal is easier to cover the surface of the low density coal. In the neutral environment, the surfaces of the low density coal and the fine mud are negatively charged. When the pH is lower than the isoelectric point of the low density coal, the zeta potential of the low density coal surface is negative, and there is an electrostatic adsorption between the low density coal and the fine coal.