The invention discloses a double antitheft lock structure comprising a lock body and a gear key. A shell is arranged outside the lock body. A keyhole is formed in the middle of the shell. Four sets of gear assemblies are evenly installed in the shell and comprise gears and transmission racks. The gears and the transmission racks are all fixedly installed on the shell through bolts. Gear teeth are distributed on the edges of the gears in a confined mode. The sides, making contact with the gears, of the transmission racks are provided with teeth meshing with the gear teeth. The lower ends of the sides, not making contact with the gears, of the transmission racks are provided with ball guide grooves. Triangular clamping blocks are arranged on one sides of the ball guide grooves. Right angle clamping blocks are arranged on the other sides of the ball guide grooves. Four balls are arranged in the middles of the ball guide grooves transversely. The double antitheft lock structure is simple in structure and reasonable in design, a lock hole can be sealed when the key is not inserted, the inside of the lock hole is prevented from being filled with foreign matter and is prevented from being blocked, meanwhile, the key needs to be modified, or a special key is used for unlocking, and antitheft performance of a lock is improved.