The invention relates to the technical field of edge milling machine machining equipment, in particular to an edge milling machine workpiece automatic positioning mechanism which comprises a left support, a base and a right support, the left support is fixedly welded to the left side of the upper end of the base, and the right support is fixedly welded to the right side of the upper end of the base. Two sets of connecting plates are welded and fixed between the left support and the right support, a base is fixed to the upper ends of the connecting plates through screws, and a hydraulic oil cylinder is rotationally connected to the base. The device is matched with an automatic control system of an edge milling machine truss to carry out station adjustment on a workpiece, automatic machining of the workpiece is achieved, a safer working environment is provided, the labor intensity of workers is reduced, the labor risk is reduced, the workload in the technological process is reduced, the enterprise competitiveness is improved, the labor condition is improved, and the production efficiency is gradually improved. And the production capacity is stronger and controllable, the upgrading of products is accelerated, the product quality is improved, boring and odorless work is eliminated, and the labor force is saved.