Syndiotactic polystyrene (sPS) and polyethylene were comparatively synthesized with homogeneous catalytic systems composing η5-pentamethycyclopentadienyltribenzyloxy titanium [Cp*Ti(OBz)3] and various modified methylaluminoxanes (mMAO).The content of TMA in mMAO can be controlled by regulating H2O/TMA molar ratio during the preparation of mMAO by partial hydrolysis of TMA with Al2(SO4)3·18H2O.The effect of Al/Ti molar ratio on polymerization of styrene as well as ethylene have been studied in detail. The oxidation states of titanium in Cp* Ti(OBz)3/MAO catalytic systems were determined by redox titration method. It seems that active centre of Ti(Ⅲ) is favorable for styrene syndiospecific polymerization with higher catalytic activity

while Ti(Ⅳ)center is favorable for ethylene polymerization.The styene syndiospecific polymerization may also be nifluenced by the external addition of tri-isobutyl-aluminum(TIBA) into the same catalytic sistem giving higer yiela but slightly lower molecuar weight of sPS.