The present invention relates to a vehicle dynamic control system for improving handling stability by controlling a dynamics of the vehicle. An object of the present invention is to provide a rear wheel toe angle control system (60), in which as an actuator (62) for controlling rear wheels (54,55) of a vehicle, an electric-powered one is used for rapid operation thereof, thereby ensuring handling stability, the left and right rear wheels are operated by the single actuator to reduce weight and manufacturing costs of a vehicle, and toe angles of the left and right rear wheels are identically controlled to improve handling stability of a vehicle. According to the present invention for achieving the objects, there is provided a rear wheel toe angle control system of a vehicle, comprising left and right rear wheels supported by a cross member (52) of a vehicle; left and right link members (64,65), each link member having an end connected to the left and right rear wheels; a rack bar (67) having both ends respectively connected to the left and right link members; a case (66) installed to the cross member to receiving the rack bar; and an actuator installed to the rack bar to cooperate therewith, the actuator moving the rack bar so that the left and right link members change toe angles of the left and right rear wheels at the same time. The actuator includes a driving motor (622) installed in a housing; a ring gear (624) to be rotated by the driving motor; a first pinion gear (625) meshed with the ring gear; and a second pinion gear (627) installed to a rotary shaft (626) of the first pinion gear and meshed with the rack bar.