The invention belongs to the technical field of K-TIG welding guns and discloses a magnetic control K-TIG welding gun based on water-cooled permanent magnets. The magnetic control K-TIG welding gun mainly comprises a cover body and a holding body connected to the lower portion of the cover body. The cover body and the holding body form a closed space and are fixed to the gun head of the welding gun. The radially and evenly distributed permanent magnets are arranged in the closed space, and water cooling devices are arranged around the permanent magnets. According to the magnetic control K-TIG welding gun, the permanent magnets are used for replacing electromagnets to construct a circular magnetic field to compress K-TIG welding electric arcs, thus the restraining effect and penetrability of the electric arcs can be enhanced; and meanwhile, the water cooling devices are arranged to wrap the permanent magnets so as to achieve the purposes of in-time cooling and demagnetization reduction, thus the stability of the obtained magnetic field is improved, and the electric arcs are restrained and controlled better.