The carboxyl-functionalized polystyrene (poly(styrene-co-methacrylic acid), PSMAA) nanofibers with average diameters of 250 +/- 20nm was prepared by electrospinning. PSMAA nanofibrous membrane were employed for immobilization of horseradish peroxidase (HRP) enzyme on the fibrous surface by a chemical method. The parameters about immobilizing HRP on the PSMAA nanofibers were studied and the influence on the activity of the HRP is discussed. This study showed that soap-free emulsion method is an ideal technology to modify the polystyrene surface and ultimately achieve enzyme immobilization on electrospun PSMAA nanofibers surfaces. Compared with free HRP, the acid-base stability, thermal stability, and storage stability of HRP were increased after the immobilization. The immobilized HRP maintained about 60% of its initial activity during a 20-day storage period. However, the free HRP maintained only 40% of its initial activity. The removal percentages of o-methoxyphenol (OMP) reached 80.2% after 120 min for immobilized HRP. These results suggest that the proposed scheme for immobilization of HRP has potential in industrial applications for the treatment of phenolic wastewater.