PAN based carbon fibers (TOTO IM6006K) were electrochemically treated in acidic and salt like electrolytic solution at different temperatures. The surface characters of the carbon fibers were characterized by SEM,XPS, adsorption of methylene blue (MB+ ) and Raman spectra. Experimental results indicated that more functional groups and deeper grooves generated on the surface of carbon fibers after electrochemical treatment. Variation of electrolytes and temperatures can affect the configuration of specific functional groups, the difference of formed amounts of hydroxyl and carboxyl groups are 61. 38% and 98. 59% at most. More acidic functional groups and roughness appeared on the surface of the carbon fibers treated in acidic electrolyte solution, and further,higher solution temperatures were helpful to improve oxidative etching on surface of carbon fibers by active oxygen. Superficial crystallite size of the treated carbon fibers decreased by 9. 75% at most.