The invention relates to an ethylene oligomerization catalyst composition which comprises a chloride 2-benzoxazolyl-6-acetyl condensed amino ferrite (II) complex shown in formula I, an aluminum-containing promoter and tert-butyl hydroperoxide. The invention further provides an ethylene oligomerization method. The ethylene oligomerization catalyst composition provided by the invention is applied to ethylene oligomerization, and is high in reaction activity at low temperature in the presence of low Al/Fe, that is, the reaction activity is up to 1.62*10<7>g.mol (Fe)<1>.h<1>.