Abstract: In order to make known the change of surface property of long-flame coal, a low-rank coal, before and after flotation, a density and size analysis of the coal is first made. It is observed through analysis that the density and size consists of the coal are predominately in a range of 1.3-1.4 g/cm³ and 0.25-0.5 mm respectively. Then flotation rate test made with coal sample reveals that the coal belongs to a moderately floatable coal. Result of analysis of the variation of surface property of long-flame coal using Fourier transform infrared spectrometer (FTIR). X-ray photoelectron spectrometer (XPS), zeta-potential meter and automatic specific surface area meter indicates that: in comparison with the raw coal, the concentrate yielded through flotation has a higher content of carbon and a reduced content of oxygen; the absolute value of zeta-potential and specific surface area both drop down; the concentrate J1 obtained at initial flotation stage and the concentrate J4 yielded at the final stage all show a decrease in the amount of oxygen functional groups; and the concentrate J3 has a highest content of carbon of up to 81.51% and a lowest content of oxygen which is only 17.34%. It is proposed at the end of the paper that stress needs to be placed on the R & D of the flotation reagent which is highly adaptable to change of surface property of low-rank coal.