Three mono-cyclopentadienyl metal complexes, [C6H4O2]CpTiCl(Ⅰ), [C12H8O2]CpTiCl (Ⅱ), and[C20H12O2] CpTiCl (Ⅲ), were prepared via the reactions of cyclopentadienyl titanium trichloride with catechol, 2,2i-bisphenol, and 2,2’-bisnaphthol, respectively. In the presence of a moderate amount of methylaluminoxane (MAO), the complexes exhibited catalytic activities for ethylene polymerization. Complex I showed the highest activity at Al/Ti molar ratio of 500 at the temperature of 30℃. With increasing of polymerization temperature, catalytic activities and molecular weight of the obtained polyethylene tended to decrease, and molecular weight distribution of polyethylene became narrower. With the molecular simulation method, the charges on titanium atoms of complexes Ⅰ, Ⅱ, and Ⅲ, and the bond angles formed by Ti and bisphenoxy ligands were calculated. It was concluded that the smaller the net charge on Ti and the smaller the angle of O1-Ti-O2, the higher the activity of the complex. (C12H8O2) CpTiCl (II), and [C20H12O2] CpTiCl (III), were prepared via the reactions of cyclopentadienyl titanium trichloride with catechol, 2,2i-bisphenol, and 2,2’-bisnaphthol, respectively. In the presence of a moderate amount of methylaluminoxane (MAO), the complexes exhibit catalytic activity for ethylene polymerization. Complex I showed the highest activity at Al / Ti molar ratio of 500 at the temperature of 30 ° C. With increasing polymerization temperature, catalytic activities and molecular weight of the polyethylene for tended to decrease, and molecular weight distribution of polyethylene as narrower. With the molecular simulation method, the charges on titanium atoms of complexes I, II, and III , and the bond angles formed by Ti and bisphenoxy ligands were calculated. It was concluded that the smaller the net charge on Ti and the smaller the angle of O1-Ti-O2, the higher the activity of the comple x.