A series of new neutral arylnickel(Ⅱ) phosphine complexes bearing non-symmetric bidentate chelate ligands, 3-aryliminomethy1-5-chloro-2-hydroxybenzaldehyde, have been synthesized,and the structure of representative complexes (2b and 2d) has been confirmed by X-ray crystallographic analysis. These neutral arylnickel(Ⅱ) phosphine complexes have been investigated as catalysts for ethylene oligomerization.Using methylaluminoxane (MAO) as a cocatalyst,these complexes display high ethylene oligomerization activities.A catalytic activity of up to 4.6×106g/mol 1h 1 has been observed. The influence of Al/Ni molar ratio, reaction temperature, reaction period and pressure on catalytic activity was investigated.