The invention discloses a refinery gas hydrogenating combined method which comprises the following steps: (a) mixing diesel oil raw oil and circulation oil with hydrogen in hydrogen dissolving equipment and then sending into a hydrogenating catalyst bed layer in a diesel oil hydrogenating reactor to react under the liquid-phase hydrogenating operation condition; (b) mixing reaction product flow obtained in step (a) with the refinery gas and hydrogen in gas dissolving equipment and then sending into a hydrogenating catalyst bed layer in a supplementary hydrogenating reactor to react under the liquid-phase hydrogenating operation condition; (c) separating hydrogenating reaction efflux in step (b) into a gas phase and a liquid phase, removing hydrogen sulfide from the separated gas phase, then continuing to separate to obtain hydrogen and the hydrogenated refinery gas, fractionally distilling the separated liquid phase to obtain naphtha and diesel oil products and utilizing a part of hydrogenating reaction efflux obtained in step (a) and/or a plurality of hydrogenating reaction product flow obtained in step (b) and/or a part of liquid phase separated by a high-pressure separator as circulation oil to return the hydrogen dissolving equipment. The method can simultaneously hydrogenate refinery gas and produce clean diesel oil.