A suitable Ziegler-Natta catalyst was prepared by supporting TiCl4 on sodium montmorillonite (Na+MMT) modified by butyl octyl magnesium (BOM). This catalyst was applied for the polymerization of ethylene toward a polyethylene (PE)/Na+MMT nanocomposite. Catalyst behavior and nanocomposite properties were studied. It was found that catalyst activity was acceptably high. In addition, it had a smooth rate during ethylene polymerization. Transmission electron microscopy image and X-ray diffraction pattern evidenced an excellent exfoliation of the Na+MMT layers in the polymer matrix.