The invention relates to an ethylene oligomerization catalyst composition and an application thereof. The composition comprises the following components: a component a contains chromium acetylacetonate, tetrahydrofuran chromium chloride and / or chromium 2-ethylhexanoate; in the formula of a component b, R1, R2, R3 and R4 are phenyl, benzyl or naphthyl; and R5 is isopropyl, butyl, cyclopropyl, cyclopentyl, cyclohexyl or fluorenyl; a component c contains methyl aluminoxane, ethyl aluminoxane, propyl aluminoxane and / or butyl aluminoxane; a component d has a formula X1R6X2, wherein X1 and X2 are F, Cl, Br, I or alkoxy, and R6 is alkyl or aryl; in the formula of a component e, R is a linking group and selected from alkyl and derivatives thereof as well as aryl and derivatives thereof; and the molar ratio is 1: (0.5-10): (50-3000): (0.5-10): (0.5-10). The catalyst has the catalytic activity being more than 5.0*10<6>g mol<-1>Cr.h<-1>, and the mass of 1-hexene and 1-octylene is more than 93%.