The utility model relates to an online detection and rejection device for changeable cigarette code stamps. The device comprises a CCD (charge coupled device) system, an image processing device, an IPC (industrial personal computer), an alarm stop device and a cigarette rejection device, wherein the CCD system comprises a trademark stamp detection CCD and a code stamp detection CCD, the trademark stamp detection CCD and the code stamp detection CCD are arranged on one side of a stamped paper tape and connected to the image processing device respectively, the image processing device is connected with the IPC, and the IPC is connected with the alarm stop device and the cigarette rejection device respectively. The device can be used for performing online one-by-one complete-inspection on the cigarette code stamps which are thin in stroke and small in character, and a quick switching function for frequent changes of the cigarette code stamps by month, by day and by shift is added, so that the working efficiency and the detection accuracy are improved.