The present invention relates to a vehicle door latch system, more particularly, relates to a vehicle door latch system comprising: a locking member spring applying an elastic force to the locking member in the opposite direction of an external force when the locking member is moved by the external force; a locking guide member rotatably installed in a housing; and a cam-part formed in a locking member for guiding the locking guide member and formed with a stopping slot; so that the structure of the device becomes simple, and at the same time, releasing of the locking member is prevented when the latch is rotated by the main gear even when the locking member is moved by the same main gear used for the latch.