Ethylene polymerization was performed with the TiO2 nanotube supported metallocene catalytic system. The effects of Al/Zr molar ratio and time in polymerization on the catalytic behavior of the catalysts and the morphologies of the polyethylene were investigated. The nanofibers, floccules and nanosheets of polyethylene were obtained by controlling the polymerization conditions. Because the nanotubes confined the direction of propagation of the polyethylene chains, nanofibers were attained by extrusion polymerization, while the amount of floccules increased with extended polymerization time and nanosheets were mainly produced at high Al/Zr molar ratios. The possible correlation between the polymerization conditions and polyethylene morphologies was elucidated. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 812-817, 2011