The present invention relates to a catalyst composition for 
ethylene oligomerization and the use thereof. Such catalyst composition includes 
chromium compound, ligand containing P and N, activator and accelerator; wherein the 
chromium compound is selected from the group consisting of acetyl 
acetone chromium, THF-chromium 
chloride and Cr(2-ethylhecanoate)3; general formula of the ligand containing P and N is shown as:in which R1, R2, R3 and R4 are phenyl, benzyl, or naphthyl. R5 is 
isopropyl, butyl, cyclopropyl, cyclopentyl, cyclohexyl or fluorenyl; the activatior is methyl 
aluminoxane, ethyl 
aluminoxane, propyl 
aluminoxane and / or butyl aluminoxane; the accelerator is selected from the group consisting of 1,1,2,2,-
tetrachloroethane, 1,1,2,2-
tetrabromoethane, 1,1,2,2-tetrafluoroethane, and compounds having a formula of X1R6X2, in which X1 and X2 are F, Cl, Br, I or alkoxyl, R6 is alkylene or 
arylene group; the 
molar ratio of chromium compound, ligand containing P and N, activator and accelerator is 1:0.5˜10:50˜3000:0.5˜10. After mixing the four components mentioned previously under 
nitrogen atmosphere for 10 minutes, they are incorporated to the reactor, or these four components are incorporated directly into the reactor. Then 
ethylene is introduced for oligomerization. Such catalyst can be used in producing 1-
octene through 
ethylene oligomerization. It is advantageous in high catalysing activity, high 1-
octene selectivity, etc. The catalytic activity is more than 1.0×106 g product·ma−1 Cr·h−1, the fraction of C8 linear α-olefin is more than 70% by 
mass.