A series of well-defined functional polyethylene graft copolymers with high molecular weights have been conveniently synthesized via the combination of ethylene/5-norbornene-2-methyl propargyl ether (NMPE) copolymerization using bis(beta-enaminoketonato)titanium catalysts and following click coupling reaction. Bis(beta-enaminoketonato)titanium catalysts have been proved to be the potent catalysts for ethylene/NMPE copolymerization, producing high molecular weight copolymers with unimodal molecular weight distributions. C-13 NMR (dept) and H-1 NMR spectra reveal the copolymerization proceeds in a regioselective way with allcynyl group retained near the main chain. The following click coupling reactions between ethylene/NMPE copolymer and azido-terminated polymer (PEO-N-3, PS-N-3) have been achieved under mild conditions independent of the chemical structure and molecular weight of azido-terminated polymer, providing functional polyethylene with well-defined structure and high molecular weight.