Chitosan (CTS) was selected to combine Fe3O4/CNTs with noncovalent bonds to prepare CTS modified magnetic carbon nanotubes (CTS-Fe3O4/CNTs). The chemical structure, morphology, crystal structure, element and magnetic properties were analyzed by means of FTIR, TEM, XRD, XPS and VSM. CTS-Fe3O4/CNTs was used as immobilized enzyme carrier for the degradation of phenolic compounds in sewage. The results of characterizations demonstrated that CTS had successfully modified the surface of Fe3O4/CNTs, amino groups existed simultaneously on the surface of Fe3O4 and CNTs. The surface modification of CTS did not destroy the crystal structure of Fe3O4/CNTs and CTS-Fe3O4/CNTs had super paramagnetic property. The effects of preparation and reaction conditions of CTS-Fe3O4/CNTs immobilized enzyme were investigated. Compared with free enzyme, the carrier CTS-Fe3O4/CNTs immobilized enzyme restricted conformational change of enzyme and stabilized enzyme relative activities, enhanced higher temperature tolerance, wider pH value, repeated using times and storage time under the optimum conditions of immobilized enzyme.