The invention relates to a method for combined hydrogenation of heavy oil. The method adopts an online hydrogenation combined process of a boiling bed and a fixed bed, light oil obtained by hydrogenation of the boiling bed does not undergo the processes of pressure reduction and frictional distillation, light oil gas phase lower than 350 DEG C obtained by a warm high-pressure separator directly enters a fixed bed reactor for hydrogenation reaction, thus avoiding the defect of complex process caused by the procedure of firstly performing product pressure reduction and separation and then performing pressure-rising and temperature-rising hydrogenation of a conventional offline hydrogenation combined process, reducing the content of wax oil component in the light oil of the fixed bed reactor,and improving the selectivity of the hydrorefining reaction. In addition, the method also has the advantages of being high in light oil yield, small in catalyst consumption, reasonable in energy utilization, compact in process flow and low in device energy consumption.