The invention belongs to the technical field of marine high-pressure-environmental electromechanical control and particularly discloses a mechanical switch-type depth sensor which includes a shell body, a piston, a magnet assembly, a spring, a switch assembly and a rubber cable terminal. The shell body is hollow in structure. The piston is slidingly disposed inside a central hole of the shell body. One end of the piston is position-limited by an inner limit opening arranged inside the shell body. One end of the shell body is provided with external threads and the other end of the shell body is connected to the rubber cable terminal. A switch assembly is disposed in the rubber cable terminal. The magnet assembly is disposed on the other end of the piston and is corresponding to the switch assembly. The spring is arranged in the central hole of the shell body and between the piston and the rubber cable terminal. The depth sensor is large in pressure set range, is stable in performance, is safe and reliable, is compact in structure, is low in cost and is easy to manufacture.