The polymerization of norbornene has been investigated in the presence of two novel bispyrazolylimine dinickel(II) complexes bis-2-(C3HN2Me2-3,5)(C(Ph) = N(4-RC6H4)Ni2Br4 (complex 1, R = H; complex 2, R = OCH3) activated by methylaluminoxane. The two catalytic systems show high activity (up to 1.83 x 10(6) gPNBE/(molNi center dot h)) for norbornene polymerization and provide polynorbornene (PNBE) with higher molecular weights (M (w) = 4.44 x 10(5)-11.57 x 10(5) g/mol) and narrower molecular weight distributions about 2.0. The electron-donating of methoxyl group in complex 2 could enhance the catalytic activity for norbornene polymerization, however, the molecular weights of polymers were decreased. The influences of polymerization parameters such as polymerization temperature, Al/Ni molar ratio, reaction time and catalyst concentration on catalytic activity, and molecular weight of the PNBEs were investigated in detail. The obtained PNBEs were characterized by means of H-1 NMR, FTIR, and thermogravimetric analyses. The analyses results of PNBE indicated that the norbornene polymerization is vinyl-type polymerization rather than ring-opening metathesis polymerization.