The invention relates to a preparation for carbon fiber paper used for a gas diffusion layer of a proton exchange membrane fuel cell, which comprises the following steps: (1) carrying out water treatment on asphalt base carbon fiber, and carrying out activation treatment on PAN base pre-oxidized fiber; (2) chopping the fibers; (3) mixing the chopped fibers, and then carrying out wet papermaking forming to obtain raw paper; (4) dispersing carbon nano tubes and/or conductive carbon black grains in resin solution; (5) spraying the resin solution on the upper surface and the lower surface of the raw paper, drying the raw paper and then thermally pressing the raw paper into a semi-finished product; and (6) thermally treating the semi-finished product to obtain the carbon fiber paper. The preparation has simple process and low cost, and is suitable for industrialized production; and the carbon fiber paper has good electric conductivity, high porosity, smooth surface, compact structure and proper flexibility and rigidity.