A plug-in mechanism, a subrack and a finished board are provided. The plug-in mechanism implements fast and reliable plug-in and plug-out by using a lever assistance effect and a gearing effect of a gear. The plug-in mechanism is configured to be disposed between a sub-carrier frame and a parent carrier frame to implement plug-in and plug-out of the sub-carrier frame in the parent carrier frame, and the plug-in mechanism includes a driving part and a gearing part, where the driving part includes an ejector lever, the gearing part includes at least one gear that is engaged successively, a gear at one end is connected to the ejector lever, each of the at least one gear is fastened onto the sub-carrier frame by using a rotating shaft, and the at least one gear is connected to the parent carrier frame by using a linkage structure.