The research on nickel complexes has provided the great potentials of new catalysts for ethylene reactivity (oligomerization and/or polymerization).In addition to studying the mechanism of catalytic ethylene reactivity

nickel complex catalysts provide the fundamental bases of model catalysts

which present certain catalytic performance including catalytic activity

selectivity for oligomer or polymer

polymer properties and so on.The well modified model catalysts and newly designed ones would pave the way for potential industrial processes.Moreover

nickel catalysts are found to be relatively easier to conduct β-hydrogen elimination and therefore they would make chances of getting novel branched polyethylenes with some advantage properties for further application.Fundamental research makes the future of industrial catalysts.The progress of nickel complexes as catalysts for ethylene reactivity are reviewed

and the intrinsic relationship between catalyst structure and corresponding catalytic performance is highlighted in this paper.