Abstract: An on-line detection system for defects of an MEA is provided. The detection system includes a workbench, two connecting rods are arranged inside the workbench, two ends of the two connecting rods are both connected to two side walls of the workbench by means of bearings, and conveying rollers are fixedly arranged outside the two connecting rods in a sleeving manner. One side of the workbench is fixedly provided with a first electric motor, and an output end of the first electric motor is fixedly connected to one of the connecting rods. Belt pulleys are fixedly arranged outside the two connecting rods in a sleeving manner, and a belt is arranged outside the two belt pulleys in a sleeving manner. A hollow roller is arranged on an inner side of the workbench, and a plurality of exhaust holes are provided in a top of the hollow roller.