A paper feeding mechanism includes a mechanical frame, a gear assembly, a paper supply tray, a pickup assembly, a paper pressing assembly and a stopper assembly. The gear assembly includes a drive gear and a transmission gear. The paper pressing assembly includes a paper pressing frame, a paper pressing tray, a gear shaft, at least one swing arm and an elastic element. The stopper assembly includes a blocking element and a connecting element. The drive gear drives the transmission gear and the gear shaft to rotate, the connecting element drives the blocking element to move downward to make the blocking element realize a paper blocking function, and the drive gear breaks away from the drive gear, the elastic element pushes against the paper pressing tray to move downward, the blocking element breaks away from the paper supply tray to raise up for making the paper blocking function disappeared.