The adsorption of the microorganisms on the surface of raw fat coal was researched, choosing bacteria FML and yeast RH which screened from lignite and hydrophobic Mycobacterium phlei (M. ph) for comparison. The influences of pH, slurry concentration and cell concentration on adsorption were analyzed. The results showed that the adsorption reached saturation in about 20 min. FML were found to follow the monolayer adsorption, similar to M. ph, while RH followed multilayer adsorption to a great degree. The adsorption of yeast RH was tested to be stable at pH=4?6 for the actual flotation system, and the adsorption rate and adsorption capacity were 82% and 3.2 mg/g, respectively. RH mainly adhered on the surface of clean coal particles and caused coal to be more hydrophobic, while the role of FML were mainly to make raw coal gangue more hydrophilic. The roles of both increased the raw coal floatability of different components and improve the flotation efficiency.