A method for improving offset paper ash content by combination of soybean protein with a filler modification reinforcing agent comprises the following steps: (1) slowly adding soybean protein into water with a temperature of 50-70 DEG C, fully stirring for 20-40 min to prepare a solution with a percent concentration of 1%; (2) adding the prepared soybean protein with a percent concentration of 1% into a pulper for bleached chemimechanical pulp according to an amount of 1-4 kg/t pulp; (3) adding the bleached chemimechanical pulp with soybean protein into a pulp preparation pool according to a mass fraction of 20%; (4) adding a filler modification reinforcing agent into diluted ground calcium carbonate according to an amount of 1-4 kg/t pulp, well mixing; (5) adding the ground calcium carbonate modified by the filler modification reinforcing agent in step (4) into the pulp obtained in step (3). When compared with other methods, the production process for improving offset paper ash content by combination of soybean protein with a filler modification reinforcing agent of the invention has the advantages of high paper ash content, large paper thickness, high paper stiffness, high surface strength, and the like.