The invention discloses a water-cooling heat dissipation device which is a hexahedron of an irregular front-rear face structure. The hexahedron is tightly attached to the upper face of a thyristor to be cooled, the thyristor is a semi-conductor device provided with four or more layers of P layers and N layers which are arranged in a staggered mode, and first openings are formed in the regions, relative to the N-type semi-conductor layers serving as cathodes, in the P-type semi-conductor layers making contact with the N-type semi-conductor layers serving as the cathodes. The half-surrounding type water-cooling heat dissipation device comprises a thyristor heat dissipation device and a damping resistance heat dissipation device and a connector (5). The damping resistance heat dissipation device and the thyristor heat dissipation device are integrated in the irregular hexahedron, and the damping resistance heat dissipation device half surrounds the thyristor heat dissipation device. By means of the water-cooling heat dissipation device, the size of a water cooling system is contracted greatly, the structure of a converter valve is simplified, connection openings of the water cooling system are reduced, the water capacity of the water cooling system is increased, and the reliability of the water cooling system is improved.