The invention discloses a modification method for improving the ash content of paper and paper strength during the high concentration filling process in starch modification. The method comprises the following steps: fully gelatinizing starch at a certain speed, then adding gelatinized starch into a fatty acid solution, carrying out reactions fully, after reactions, adding evenly stirred high concentration filling material suspension, fully mixing to carry out reactions, after reactions, adding a calcium salt solution, and after reactions, obtaining a modified filling material for papermaking, wherein the papermaking filling material can be applied to paper filling. The unutilized rate of raw materials is controlled to be less than 5%, and dissolved starch is very little. Under a same strength condition, when the provided modified filling material is used to fill paper with an ash content of 30 to 35%, the ash content of the paper can be increased to more than 40%. Under a same ash content, when the modified filling material is used to fill paper, the strength of filled paper is improved by more than 35%, compared with unfilled paper, and the using amount of fibers and production cost are effectively reduced.