The invention relates to an ethylene oligomerization method, characterized by using chlorinated 2-acetyl-1, 10-phenanthroline condensation-amine poly post transition metal (II) complex of formula (I) or (II) as a main catalyst, wherein, M represents a post transition metal, preferred Fe2+, Co2+ or Ni2+, R represents 1-naphthyl or dibenzyl methyl, and R1-R5 respectively represents H, C1-C6 alkyl, halogen, C1-C6 alkoxy or nitryl. In the method, an ethylene oligomerization temperature ranges from -10 to 19 DEG C, preferred 0 to 15 DEG C, and more preferred 5 to 10 DEG C. Compared with the prior art, the ethylene oligomerization disclosed herein has high activity and few generated polymer. The invention has a wide industrial prospect.