The invention provides a method for improving heavy oil quality and increasing light oil yield and belongs to the technical field of the energy chemical industry. According to the method, on the basisof the characteristic that an Ni-based catalyst catalyzes methane reforming and heavy oil cracking simultaneously, methane-rich gas and heavy oil (or an oil product rich in heavy oil) are subjected to a reaction on the Ni-based catalyst simultaneously, coupling quality improvement is realized, and the purposes of improving heavy oil quality and increasing light oil yield simultaneously are achieved. The method solves the problems of obvious reduction of oil yield, limited increase of light oil product yield and the like in a traditional conversion process from heavy oil to light oil and has the great significance for improving the heavy oil quality and solving the problems of system blockage and the like caused by high content of heavy components, and a new way is provided for comprehensive utilization of methane.