A monocyclopentadienyl titanium complex containing 8-quinolinolato (QCpTiCl_2) was synthesized. Its activities in ethylene polymerization at various Al/Ti molar ratios, different temperatures and activation time were investigated. The activity with a Al/Ti molar ratio of 500 exhibited a maximum of 2.8×10~5 g/(mol.h) at 30℃. The activation time of QCpTiCl_2 with MAO before polymerization also plays a role on the activity. The structural properties of the produced polyethylene (molecular weight, molecular weight distribution and melting point) were discussed. Kinetic behaviors of ethylene polymerization with the QCpTiCl_2/MAO system at different Al/Ti molar ratios were studied. For the QCpTiMeCl/MAO system and the CpTiMe_2Cl/MAO system, binding energies of the examined intermediates were calculated by quantum-mechanical method based on ADF program, respectively. It is confirmed that the chlorinebridged adduct formed by the reaction of QCpTiMeCl with MAO is thermodynamically steady. In the case of the QCp Its activities in a molar ratio of Al / Ti molar ratio of 500 exhibited a maximum of The activation time of QCpTiCl_2 with MAO before polymerization also plays a role on the activity. The structural properties of the produced polyethylene (molecular weight, molecular weight distribution and melting point ) were discussed. Kinetic behaviors of ethylene polymerization with the QCpTiCl_2 / MAO system at different Al / Ti molar ratios were studied. For the QCpTiMeCl / MAO system and the CpTiMe_2Cl / MAO system, binding energies of the reviewed intermediates were calculated by quantum-mechanical method based on ADF program, respectively. It is confirmed that the chlorine bridged adduct formed by the reaction of QCpTiMeCl with MAO is thermodynamically steady. In the case of the QCp