A robot arm assembly includes a main base, a joint and at least one arm. The main base includes a main body, and the main body includes a mounting portion and a limiting post on a side of the mounting portion. The joint is rotatably mounted on the mounting portion and includes a limit piece corresponding to the limiting post. The at least one arm is fixed to the joint, when the arm rotates relative to the main base to a predetermined extent of rotation, the limit piece abuts against the limiting post to stop the rotation of the arm.