The present invention relates to a lower arm for vehicle suspension system comprising a first bush mounting part and a second bush mounting part mounted to a front member mounting assembly of a vehicle chassis to be spaced apart therebetween at front and rear, a first arm having one end part connected to the first bush mounting part and the other end part extruding laterally from the vehicle chassis to be connected to a ball joint mounting part to support a wheel mounting assembly, and a second arm having one end part extending integrally from the first arm and the other end part connected to the second bush mounting part, wherein the first arm is formed by forming a metal plate, the one end part of the first arm connected to the first bush mounting part has a pair of ring members which are formed by forming the metal plate to be parallel therebetween in an axial direction and to contact and support through their inner round surfaces an outer round surface of the first bush mounting part. Therefore, welding parts are removed in the manufacturing process so that easy manufacturing, high strength and weight reduction compared to the conventional art can be accomplished.