(CpCH_2CH_2CH = CH_2)_2MCl_2(M=Zr, Hf)/MAO and Cp_2ZrCl_2/MAO (Cp=cyclopentadienyl; MAO=methylaluminoxane) catalyst systems have been compared for ethylene copolymerization to investigate the influence of theligand and transition metal on the polymerization activity and copolymer properties. For both CH_2CH_2CH=CH_2 substitutedcatalysts the catalytic activity decreased with increasing propene concentration in the feed. The activity of the hafnocenecatalyst was 6～8 times lower than that of the analogous zirconocene catalyst, ~(13)C NMR analysis showed that the copolymerobtained using the unsubstituted catalyst Cp_2ZrCl_2 has greater incorporatien of propene than those produced byCH_2CH_2CH=CH_2 substituted Zr and Hf catalysts. The melting point, crystallinity and the viscosity-average molecularweight of the copolymer decreased with an increase of propenc concentration in the feed. Both CH_2CH_2CH= CH_2 substitutedZr and Hf catalysts exhibit little or no difference in the melting point and crystallinity of the produced copolymers. However,there are significant differences between the two zirconocene catalysts. The copolymer produced by Cp_2ZrCl_2 catalyst havemuch lower T_m and X_c than those obtained with the (CpCH_2CH_2CH=CH_2)_2ZrCl_2 catalyst. The density and molecular weightof the copolymer decreased in the order: (CpCH_2CH_2CH=CH_2)_2HfCl_2>(CpCH_2CH_2CH=CH_2)_2ZrCl_2>Cp_2ZrCl_2. The kineticbehavior of copolymerizaton with Hf catalyst was found to be different from that with Zr catalyst. (CpCH_2CH_2CH = CH_2) _2MCl_2 (M = Zr, Hf) / MAO and Cp_2ZrCl_2 / MAO (Cp = cyclopentadienyl; MAO = methylaluminoxane) catalyst systems have been compared for ethylene copolymerization to investigate the influence of theligand and transition metal on the polymerization activity and For the activity of the hanocene catalyst was 6 ~ 8 times lower than that of the analogous zirconocene catalyst, ~ (13) C NMR analysis showed that the copolymerobtained using the unsubstituted catalyst Cp_2ZrCl_2 has a greater incorporatien of propene than those produced by CH_2CH_2CH = CH_2 substituted Zr and Hf catalysts. The melting point, crystallinity and the viscosity-average molecular weight of the copolymer decreased with an increase of propenc concentration in the feed. Both CH_2CH_2CH = CH 2 substituted Zr and Hf catalysts exhibit little or no difference in the melting point and crystallinity of the produced copolymers. However, there are significant differences between the two zirconocene catalysts. The density and molecular weight of the copolymer. by Cp_ (2) decreased in the order: (CpCH_2CH_2CH = CH_2) _2HfCl_2> (CpCH_2CH_2CH = CH_2) _2ZrCl_2> Cp_2ZrCl_2. The kinetic behavior of copolymerizaton with Hf catalyst was found to be different from that with Zr catalyst.