The utility model provides an instrument of puzzle lock, the device belong to the well head and prevent burglary. The technical problem that will solve is, the expense of going into, open the bridging plug down is very high, and the theftproof effect is not good, and can not use repeatedly. The problem of its technique is solved technical scheme, a puzzle lock by main casing body group weldment, upper cover assembly welding spare, axle sleeve, spacer ring, driver plate, hanging wall, dial nail, lock, calibrated scale and constitute, the outside system of characterized by puzzle lock's shell body assembly welding spare has the casing coupling screw thread, and open inside upper end has wide groove, corresponds with the boss that locks the structure, is equipped with the elastically positioned structure between upper cover assembly welding spare and axle sleeve, installs on the driver plate and dials the nail, utilizes the rotatory upper cover of dedicated instrument, and the drive driver plate is rotatory, dial the mounted position of nail on the driver plate through changing, set for multiple password. The utility model discloses an actively the effect is: seal the well head with the device, it is functional to prevent burglary to can repetitious usage, reduced the expense of shut -in well.