Abstract: A study is made on the surface property of long flame coal through Fourier transform infrared spectroscopic analysis,XPS analysis,potentiometric analysis and the use of automatic specific surface area measuring apparatus. It is found that the relative proportion of oxygen element in long flame coal is as high as 28. 04 percent while the proportion of C in C—O, C＝O and COO— hydrophilic group accounts for 43. 26 percent of the total in flame coal,and the C element is of a porous structure with a specific surface area reaching 2. 650 9 m²/g. It indicates that long flame coal is poor in hydrophobicity and flotability. As revealed by analysis of the FTIR spectrums of 5 different kinds of collectors,the collector containing a certain amount of such unsaturated-bond group as —OH, C＝O can combine with the oxygen-containing groups on low-rank coal surface through weak oxygen bonds,increasing,therefore,the hydrophobicity of the surface of the low-rank coal due to absorption of the long-chain groups of the nonpolar hydrocarbon C—C and C—H onto the coal surface. It can be inferred through the variation of the XPS spectrum of the coal surface. It can be inferred through the variation of the XPS spectrum of the coal particles before and after the reaction of flotation reagent with the low-rank coal,the absorption of flotation reagent on surface of low-rank coal is essentially a kind of physical absorption. It is proposed at the last that,for the flotation of low-rank coal,the development of flotation reagent be specifically made according to the surface property of the coal.