Hydrophilic modification of polypropylene microfiltration membranes was performed with the introduction of peroxide onto the membrane surface by ozone treatment followed by graft polymerization with hydroxyethyl methacrylate (HEMA). The grafting was initiated at a mild temperature by redox decomposition of the peroxide. The ozone treatment time was optimized in the range of 3-5 min to have a degree of grafting while keeping the mechanical strength. The HEMA grafting made the surface of the PP membrane hydrophilic and less adsorbable to BSA proteins, although its effects were dependent on the ozone treatment time. The grafted membrane with 5 min ozone treatment gave greater flux recoveries (up to approximately 95%) at the end of the MF of the BSA solution, suggesting that the protein fouling layer was reversible because of the hydrophilic nature of the modified membranes.