Porous polyethylene with nanofiber structure in the form of discrete, freeflowing, micron-sized spheres was formed in high activity by ethylene polymerization with porous polymer supported Ziegler-Natta catalyst. Such versatile porous support catalyst played as a template in two levels. One level is the whole support beads, which resulted in the porous polyethylene spheres. Another level is the porous structure in the support beads, which played as a nanoreactor and resulted in the nanofiber structure in the polyethylene spheres. (C) 2010 Elsevier Ltd. All rights reserved.