Locking device used for vehicle door lock

The utility model discloses a locking device used for a vehicle door lock. The locking device comprises a shell body, a motor and a lock tongue; the lock tongue is connected with a rotating shaft of the motor by a retractor, the retractor is a Ti Ni shape memory alloy strip, and a connecting rod of the lock tongue is connected with the shape memory alloy strip by penetrating the shell body and by a hinge pin; and a spring 1 and a spring 2 are sleeved on the connecting rod, wherein the spring 1 is sleeved between the lock tongue and the outer wall of the shell body, and the spring 2 is sleeved between the hinge pin and the inner wall of the shell body. In the locking device, the Ti Ni shape memory alloy strip is adopted for replacing a worm gear and a worm drive, so that the gear surface contact fatigue and the noise caused by the matched driving of the worm gear and the worm drive are avoided; the springs are used for absorbing the power generated by the moving of the lock tongue into a lock body and providin