The invention relates to an engaging mechanism for hoisting a cable underwater robot, which is characterized by comprising a hanger. A lifting lug is arranged at the upper part of the hanger; two overturn plates are symmetrically arranged at both sides of the hanger, and are hinged on the hanger through pin shafts; a semicircular opening is arranged at the front end of each overturn plate; when the two overturn plates are in an engaging state, the front ends of the two overturn plates at the inner sides are aligned; torsion springs are sleeved on the pin shafts, one end of each torsion spring supports against the hanger, and the other end of each torsion spring supports against the outer side of each overturn plate; and two hydraulic oil cylinders are symmetrically arranged above the overturn plates, cylinder bodies of the hydraulic oil cylinders are hinged on the hanger, and the front ends of piston rods of the two hydraulic oil cylinders are respectively articulated with the outer sides of the overturn plates. The invention has simple structure, is easy to operate, can remotely control unhooking or hooking on cable underwater robot laying or recovery, can launch to manually hook or unhook for the cable underwater robot in stead of a diver, lightens the work intensity of the diver, and improves the work efficiency of distributing or recovering the cable underwater robot.