The invention relates to a workpiece automatic identification and reversed installation prevention mechanism. The mechanism comprises a tail bracket of a machine tool, wherein, the tail bracket is provided with a back-front telescopic sleeve; the mechanism further comprises a transmission block and a plurality of proximity switches and a plurality of reversed installation prevention proximity switches supporting the transmission block, wherein, the transmission block is arranged on the outside surface of the sleeve, the tail bracket is further provided with a support, the proximity switches are arranged on the support, and the proximity switches and the reversed installation prevention proximity switches are respectively connected on corresponding signal input terminals to input a connection signal thereon to a control system of the machine tool for identifying different workpieces and if the workpieces are installed in a right direction; and different workpieces are processed by automatically adjusting a corresponding processing program through the control system, thus improving the production efficiency and avoiding or reducing misoperation.