The invention discloses a method for preparing a paper-based material by bleaching KP pulp through biochemical method ECF of fast-growing poplars. The method comprises the following steps: (1) preparing paper pulp by utilizing a bleaching of the biochemical method ECF of the fast-growing poplars; (2) carrying out gradient beating on the prepared paper pulp to obtain paper pulp with three types of beating degrees, wherein the beating degree of the first paper pulp is 10 degrees SR to 30 degrees SR, the beating degree of the second paper pulp is 30 degrees SR to 55 degrees SR and the beating degree of the third paper pulp is 55 degrees SR to 70 degrees SR; carrying out papermaking molding or pressing molding on mixed pulp to obtain the paper-based material. By adopting two key technologies including a gradient beating technology and a self-adding technology, the disadvantages in a single beating technology in the prior art are overcome and the utilization of an additional additive is avoided; a prepared paper base has the advantages of high folding endurance, high breaking resistance, tearing indexes and the like; the method is suitable for preparation of various types of paper bases and is especially suitable for preparation of an environment-friendly packaging paper-based material.