The invention relates to a fire protection extinguishment technology and discloses a mechanical pressure release device. The mechanical pressure release device is characterized by comprising a window body, a fixed plate close to the outer side of the window body, a torsional spring arranged on the upper part of the fixed plate, a magnetic locking structure arranged on the lower part of the fixed plate, a baffle of which the upper end is capable of rotating around the fixed plate, and an armature arranged on the inner side of the baffle, wherein the fixed plate is fixed on the window body through an expansion bolt; the torsional spring is fixed on a rotating shaft; one end extending from the tail end of the torsional spring presses against the baffle, and the other end extending from the tail end of the torsional spring is fixed on the fixed plate; the rotating shaft is arranged on the upper part of the fixed plate through a bearing; the armature is arranged on the baffle corresponding to the magnetic locking structure. The mechanical pressure release device can be immediately started to release pressure when a gas fire extinguishment system extinguishes fire to eliminate injury caused by dramatic rising of gas pressure. The mechanical pressure release device is simple in structure, convenient to use and wide in application range.