Firstly, the flexible forming principle of rubber bag for sheet metal, the equipment structure and technical parameters were introduced, and then, the working principle of ultrahigh pressure hydraulic system was discussed in detail including the ultrahigh pressure supercharger and the ultrahigh pressure sealing technology, especially the angle sealing assembly of rectangular structure. On this basis, the control method of ultrahigh pressure hydraulic system was studied, in which the closedloop pressure control system of main pump was used to compensate the pressure loss of the system at large flow output, and the control method of highpressure transition process for supercharger was used to obtain ultraquiet effect when switching at high speed. Finally, the results were applied to the manufacture of the first domestic 770 MN rubber bag hydraulic press, which verified their advancement and reliability through more than one year of production applications.