The invention discloses a mechanical automation mould machining device. The mechanical automation mould machining device comprises mould machining equipment body and grinding equipment; a workbench isarranged in the mould machining equipment body; a height adjustment motor is arranged at the lower end of the workbench through a bracket; a height adjustment rod is arranged on one side of the height adjustment motor; the top end of the height adjustment rod penetrates through the bottom surface of the workbench to reach the upper surface of the workbench; a mould fixing block is arranged at thetop end of the height adjustment rod; a locating rod is arranged in the mould fixing block; the locating rod penetrates through the bottom end and the top end of the mould fixing block to reach the outside of the mould fixing block; and the mould fixing fixture is changed to fix a mould depending on a groove. During use, moulds in different sizes can be fixed during use, polishing operation can be carried out without changing the fixture when facing the moulds in different sizes, the time for changing the mould fixture is saved and the equipment working efficiency is improved.