The invention discloses overhead girder bottom automatic roughening equipment. The overhead girder automatic roughening equipment comprises a clamping device, a conveyor device and a roughening device. The clamping device comprises a plurality of clamping supporting mechanisms, the clamping supporting mechanisms comprise first clamping tubes and second clamping tubes, the first clamping tubes andthe second clamping tubes are correspondingly connected with first pressing plate assemblies and second pressing plate assemblies, and first bidirectional telescopic air cylinders and first supportingframes are movably connected between the first clamping tubes and the second clamping tubes. The conveyor device comprises a conveyor track plate and a first pull rope, the conveyor track plate is connected to the first supporting frames, the conveyor track plate is provided with a movable supporting plate and first vertical telescopic air cylinders, and the roughening device is arranged on the first vertical telescopic air cylinders; and the lower end of the conveyor track plate is connected with a first pull assembly and a second pull assembly. The automatic roughening equipment realizes automatic roughening of the girder bottom, and the roughening efficiency is high. The invention further discloses an overhead girder bottom roughening method. According to the roughening method, roughening for the overhead girder bottom can be carried out more effectively and conveniently through the roughening equipment.