Abstract: An blocking apparatus for gun trigger includes a main body of lock and a locking plate. The locking body is composed of a lock cylinder and a locking piece disposed inside a plastic core, then covered by a metal casing and a metal panel. The surface thereof is coated with a waterproof layer by injection molding. The locking plate has two locking rods installed on a metal plate. The surface of the locking plate is also covered with a waterproof layer by injection molding. The two locking rods on the metal plate are inserted into two inserting holes on the locking body so as to lock the trigger of gun.