To prepare the renewable carrier materials for immobilization of nitrifying bacteria, polylactic acid (PLA) dichloromethane solution was added to chitosan aqueous solution, mixed by agitation at a speed of 150 rpm / min. The resultant PLA microspheres were fund to have diameter of 100 ~ 300 μm, thus underwent ammonolysis by a 6 % hexamethylenediamine / n-propanol solution for 8 min, hydroformylation by a 1% glutaraldehyde solution for 3 h, and grafted with 1% chitosan for 24 h, to improve the surface hydrophilic property. The static adsorption was applied for adhesion of nitrifying bacteria to the surface of the carrier, i.e. immobilization of nitrifying bacteria. The removal efficiency of ammonia by the immobilized nitrifying bacteria in wastewater treatment was tested. The results showed that the surface of the microsphere carrier was rough and osteoporosis, therefore it can adhere more nitrifying bacteria. When it was immersed in the suspension of nitrifying bacteria for 8 h, the rate of nitrification by the immobilized nitrifying bacteria reached the highest level and tended to be stable afterwards.