The present invention relates to a catalyst for overhydrogenation treatment of distillate oil, specially for treating low-grade diesel oil (for example, high-sulfur naphthenic base straight-run diesel oil, coker diesel oil, coker cracked diesel oil or their mixture), and the treated diesel oil can be used as blending component of high-grade diesel oil. Said catalyst is formed from composite carrier which is obtained by high-temp. roasting the mixture of diaspore which is made up by means of alkylaluminium or oxyalkylaluminium hydrolysis method and whose purity is greater than 70% and zeolite exchanged with cation, phosphorus and active components of nickel and molybdenum, etc. and its composition includes (wt%) 2.5-8.0% of nickel oxide, 10-30% of molybdenum oxide, 0.2-4.0% of phosphorus and the rest is composite carrier.