A useful method is reported for the first time to determine the distribution of active enzyme immobilized onto surface modified porous polypropylene microfiltration membranes (PPMM). Horseradish peroxidase (HRP) was chosen as the template enzyme, the immobilization methods adopted here were either static (by soaking) or dynamic (under liquid flow) chemical binding through the reactions among linking amino groups on both membrane and enzyme by aid of glutaraldehyde. The immobilization results revealed that the dynamical method can fix more amount of enzyme on the substrate, while the specific activity of immobilized HRP is never higher. 3,3'-Diaminobenzidine tetrahydrochloride (DAB) method is introduced to the microfiltration membrane for the first time to determine the distribution of active enzymes after immobilization, the results of which were then applied to explain the difference between the two enzyme immobilization methods, which will be propitious to the development of immobilized enzyme membrane reactors. (c) 2005 Elsevier B.V. All rights reserved.