The invention discloses a petroleum coke preprocessing method for preparing a prebaked carbon anode, comprising the steps of: sieving green petroleum coke, extruding petroleum coke powder with a particle size below 3mm into spherical particles, calcining the spherical particles and coarse particles with a particle size above 3mm and applying the calcinate to preparing the prebaked carbon anode. According to the invention, fine powder in the green petroleum coke is sieved, extruded into spheres and used on the flow of preparing the prebaked carbon anode, therefore, the burning loss of the petroleum coke is decreased, the actual yield of the calinated coke can be significantly increased, the particle-size composition of the calcined coke is improved and more suitable for technological requirements and the occurrence probability of waste carbon anode with cracks is reduced. The method disclosed by the invention has the advantages of little change to the existing process, good compatibility with the existing process and simpleness in equipment and can be used for industrial production.