A fence lock consists of a lock body, a lock core, a lock bolt, a lock chain and a key, wherein the lock body has a cylindrical lock cavity, an internal thread is arranged on the wall of the lock cavity, and a through hole running through the lock cavity is formed at one end of the lock body; the lock bolt is a dumbbell-shaped cylinder with two thick ends and a fine middle section and is inserted into the through hole in the lock body; the lock core is a cylinder, the external part of which is provided with an external thread, is arranged in the lock cavity and matched with the internal thread of the lock cavity through the external thread, and can move helically front and back in the lock cavity; a U-shaped clamp is movably connected at the front end of the lock core, the lock core moves to the front end of the lock cavity, the U-shaped clamp is clamped into the middle section of the lock bolt for clamping the lock bolt, a connecting part is arranged on the rear end surface of the lock core, and the key is connected and matched with the connecting part on the lock core; and one end of the lock chain is fixed on the lock body, and the other end of the lock chain is connected with the lock bolt.