The invention provides an underwater depth-setting releasing device, which comprises a base, an upper cover, a piston, a leather bag and a rupture disk. The barrel bottom of the upper cover is provided with a through hole, glycerin is filled in the leather bag, the piston and the leather bag are placed in the upper cover, the rupture disk is clamped between the base and the upper cover which are fastened by a bolt, the side wall of the upper cover close to the barrel bottom is provided with a steel ball hole, a bearing sleeve is sleeved outside the upper cover and provided with a steel ball hole corresponding to the steel ball hole on the side wall of the upper cover, steel balls are arranged in the steel ball holes, the bearing sleeve is provided with a steel ball retainer ring, and a ballast is connected to the base. The underwater depth-setting releasing device has the advantages of relatively low cost, large bearing load, light weight, small volume, simple installation, easy detection and control, high control accuracy and the like, can be applicable and practicable in a predetermined ocean depth, and can be applied to an underwater robot, an underwater construction machine and underwater equipment.