NOVELTY - Preparing carbon fiber paper comprises adding chopped carbon fibers in acetone and then soaking with ethanol and water, taking out a drying liquid, adding chopped carbon fiber and dispersing agent into a container and then stirring, adding conductive carbon black with ethanol aqueous solution into a milling tank and then soaking, adding wood pulp and water in a pulping machine and then crushing into a pulping tank, adding obtained conductive carbon black and wood pulp in a slurry tank and then grinding and discharging.    USE - The method is useful for preparing carbon fiber paper, which is useful in porous fuel cell electrode diffusion layer material (claimed).    ADVANTAGE - The method provides carbon fiber paper with porous structure, low resistivity, high conductivity, and good mechanical strength, chemical stability and thermal stability.    DETAILED DESCRIPTION - Preparing carbon fiber paper comprises (1) adding chopped carbon fibers in a solution of acetone and then soaking with ethanol and water for 2-3 hours, where a weight ratio of the acetone, ethanol and water is 1:1:20, taking out a drying liquid, adding chopped carbon fiber and dispersing agent (0.1-0.3%) into a container and then stirring at a speed of 1000-3000 revolutions per minute (rpm) for 0.5-2 hours, (2) adding conductive carbon black (5 wt.%) with ethanol aqueous solution into a milling tank and then soaking for 3-4 hours, (3) adding wood pulp and water (5-15%) in a pulping machine and then crushing in a pulping tank, (4) adding obtained conductive carbon black and wood pulp in a slurry tank according to a weight ratio of 1:1-2 and then grinding for 1-2 hours and discharging, and adding 1-3% of the chopped carbon fiber and cationic starch (0.2-0.4%) with water and then grinding for 1-2 hours, and placing the grinded mixture into a pulping machine and then reacting, (5) adding the reacted mixture with water for 4-6 times into the slurry tank and then uniformly stirring for 20-40 minutes to obtain the slurry, and (6) drying the slurry in a paper machine at 80-90 degrees C and a speed of 1000-3000 rpm, and introducing the dried slurry and water in a paper machine according to a weight ratio of 1:1.5-2 and then drying and coiling.