The invention discloses a preparation method of a hydro-treatment catalyst. The preparation method comprises the following steps: preparing an alumina carrier, preparing an impregnation solution containing the VIII group metal and VIB group metal, wherein the impregnation solution comprises a proper amount of an organic auxiliary agent containing chelating ligand, then impregnating the alumina carrier into the impregnation solution under a proper ultrasonic treatment condition, and drying so as to obtain the hydro-treatment catalyst. The preparation method utilizes the ultrasonic cavitation effect to properly reduce the viscosity of the impregnation solution; at the same time the complexing capacity between the chelating ligand in the organic auxiliary agent and nickel / cobalt is improved by the catalytic function of the ultrasonic, the interaction force between the chelating ligand and nickel / cobalt is strengthened, thus the active metal component is promoted to highly disperse on the carrier surface, furthermore, the existing state of the active metal on the catalyst surface is improved at the same time, the sulfurization degree and sulfurization uniformity of the active metal are both improved, so the activity and stability of the catalyst are both improved. The catalyst is especially suitable for being used in the hydro-denitrogenation process and hydro-desulfurization process of heavy distillate oil.