Device for releasing pressure of jack and jack system

The invention relates to a device for releasing pressure of a jack and a jack system, and relates to the technical field of jacks. The device comprises a frame body used for being parallel to the jack, a pressing end vertically connected to the top end of the frame body and used for being pressed on the jack, a platform connected to the bottom end of the frame body, and at least one back pressure mechanism, wherein the bottom end of the back pressure mechanism is arranged on the platform, and the top end of the back pressure mechanism is used for jacking a load borne on the jack in order to enable the pressing end to apply back pressure to the jack. The load on the jack is jacked upwards through the back pressure mechanism, the back pressure mechanism bears the back pressure of the load, and the back pressure mechanism presses the platform downwards, so that the pressing end is driven to apply downward pressure to the jack to assist the jack in pressure relief and oil return, the speed of pressure relief and