Separation tests were conducted to investigate the separation performance of fine lignite by enhanced gravity concentrator. Size composition analysis illustrates that ultrafine coal with high ash content is mainly concentrated in clean coal. In addition, it also shows that ultrafine particles content increased after separation. The size composition change was explained by surface property analysis, and results show that adhesion of fragments and surface hydrophilicity that was caused by high content of oxygen functional groups are responsible for the size change. The existence of ultrafine particle is the main reason of low separation efficiency.