Abstract: In order to explore the influence of different factors on surface Zeta potential of low-rank coal, an analysis is made of the elementary composition of each of the three kinds of coal, long-flame coal, non-caking coal and gas coal. Meanwhile, the long-flame coal is taken as the object to explore the change of its surface Zeta potential in relation to such factors as particle size and density, standing time, agitating intensity and pH value. As evidenced by test result, the high-density coal sample shows a lowest Zeta potential, and the finer the size, the smaller the Zeta potential becomes; and under the identical testing conditions, and at a standing time of 2 days, an agitating time of 800r/min and a pH value of 7, the Zeta potential tends to drop with the rise of electronegativity and the higher the latter, the lower the Zeta potential becomes.