Abstract: Current experiment indicates that the activated sludge that contains abundant microorganism can be easy to immobilize on the surface of PAN-based carbon fiber(CF) when the surface of carbon fiber is modified by use of electrochemical oxidation or dynamic immobilization replaces static immobilization.Based on characterization of the surface morphology of the carbon fibers,surface oxygenic functional groups and the surface oxygen content,main influence factors which control activated sludge immobilization are analyzed. SEM results indicate that increasing surface roughness is good to biofilm formation.XPS analysis shows that C-C bond、carboxyl、carbonyl are the three main functional groups to influence the biofilm and the existence of absorbed oxygen on the surface can increase the amount of biofilm.