The invention relates to the field of solid-liquid separation, in particular to a pressing mechanism of a vertical automatic filter press. Functions such as pulling open, closing, pressing, locking and the like of the filter plate of the traditional vertical automatic filter press are respectively completed by adopting multiple groups of cylinders. The pressing mechanism has the defects of complex structure, high cost, high frequency of failures, large difficulty of maintenance works, long time, influence on production, and the like. The invention provides an opening and closing self-locking pressing mechanism directly dragged by using a motor, and functions of pulling the filter plate open, closing the filter plate, pressing the filter plate, self-locking for pressure maintenance, rapidly opening and closing and the like of the opening and closing self-locking pressing mechanism are integrated into a whole. The opening and closing self-locking pressing mechanism is matched with high and new technical products such as a frequency converter motor, a PLC (Programmable Logic Controller), a touch screen, a frequency converter, a coder and the like, and executes a digital closed-loop automatic control. The invention has the advantages of simple, compact and reasonable structure, high efficiency, energy saving, less failure factors, stable and reliable work, low cost, durability, convenience for operation and use, high operability and the like, is beneficial to popularization, promotion and application of the vertical automatic filter press, and fully develops the special advantages.