A plug-in contact assembly suitable for automatic transfer switches includes a contact holder, two moving contact pieces disposed apart from each other, a moving contact piece bracket and a biasing spring; the contact holder holds the moving contact piece bracket and the biasing spring therein; and the two moving contact pieces disposed apart from each other are held in place relative to the contact holder under the joint action of the biasing spring and the moving contact piece bracket; characterized in that, two ends of each moving contact piece are each provided with a moving contact thereon by means of welding.