The invention belongs to the field of detection of aluminum materials, and concretely relates to a method for detecting the dark strip defects of the surface of a CTP plate base. The method comprises the following steps: carrying out alkali washing on the cold-rolled CTP plate base having an exit thickness, polishing the washed CTP plate base with a sulfuric acid and phosphoric acid mixed acid, leveling and polishing the treated CTP plate base by using the difference of the dissolving speeds of the concave position and the convex position of the surface of an aluminum material in a solution to expose dark strips formed by sticky aluminum and pits in the original continuous casting and continuous rolling process, and directly observing the dark strips in common lamp lights or sunshine. The method can rapidly and accurately detect the dark strip defects having a thickness of 3-6 [mu]m below the surface layer of the plate base, avoids quality complaint caused by defective products going to downstream clients, and can realize the earlier finding of the quality defects in order to improve the quality and reduce the loss.