In the present work, poly(methyl methacrylate) (PMMA)/ montmorillonite (MMT) composite microfibers were firstly prepared by in situ emulsion polymerization combined with electrospinning, and then treated by oxygen plasma to create microfibers membrane with increased hydrophilicity and to further improve its immobilization. Conditions of plasma treatment were found for maximum laccase immobilized yield on these plasma treated microfibers’ surfaces. Scanning electron microscope (SEM) was used to investigate surface morphology of PMMA/O-MMT composite microfibers before and after plasma treatment, while the wetting behavior was studied by drop shape analyzer. The degradation of reactive red X-3B was tested to indicate the immobilization yield of laccase indirectly. The results showed that plasma treatment greatly enhanced microfibers’ surface roughness and hydrophilicity. Laccase was physically adsorbed onto the surface of PMMA/MMT composite microfibers. Besides, under the conditions of 90s(60w, 80w, 100w), the microfibers get the best immobilization yield.