The invention discloses a hydrodesulfurization and denitrification process for diesel oil. A fixed bed reactor is used in the process and is filled with a hydrodesulfurization and denitrification catalyst, and the catalyst comprises a carrier, an active component and a catalytic aid; the carrier is a compound or mixture of MSU-G, SBA-15 and HMS; the active component is a mixture of dimolybdenum nitride MO2N, tungsten nitride W2N, molybdenum carbide Mo2C and tungsten carbide WC; the catalytic aid is a mixture of Cr2O3, ZrO2, CeO2, V2O5 and NbOPO4; and the reaction conditions of the fixed bed reactor are as follows: the reaction temperature is 320-360 DEG C, the reaction pressure is 6MPa-8MPa, the hydrogen-oil volume ratio is 300-600, and the volume space velocity is 1.0h<-1>-2.5h<-1>. By virtue of the process, the total sulfur content of the diesel oil can be controlled to be lower than 5ppm, and meanwhile, the total nitrogen content of the diesel oil can be controlled to be within 10ppm.