The invention provides a method for treating diesel through hydrogenation. The method comprises the following steps: diesel raw oil enters a hydrogenation reactor from a raw oil inlet, a first reaction area and a second reaction area are arranged in the hydrogenation reactor from top to bottom, the raw oil inlet is formed between the first reaction area and the second reaction area, a hydrogen inlet is formed in the bottom of the hydrogenation reactor, a reaction effluent I is discharged from the top of the hydrogenation reactor, a reaction effluent II is discharged from the bottom of the hydrogenation reactor, after the reaction effluent I is mixed with the reaction effluent II, the mixture is separated to obtain hydrogenation generation oil, and based on the diesel raw oil, the saturation factor of polycyclic aromatic hydrocarbons in the hydrogenation generation oil is 85%-90%, and the selectivity of monocyclic aromatic hydrocarbons is 80%-85%. In the method provided by the invention, the high-quality raw materials are provided for preparing a high-octane gasoline or BTX component through catalytic cracking or hydrogen cracking, and moreover, the hydrogen consumption in the hydrogenation process is reduced, and the process economy is beneficially improved.