Abstract: This paper introduces a digital control system for submerged arc welding (SAW) applicable to various sorts of welding rectifier and feed wire device droved by direct current motor. The controllers are respectively formed with two micro-control units, of which one is used for output characteristic controlling of the power source, the other is for controlling of the feed wire speed, welding tractor and SAW processes, and exchange data by serial communication. Adopted the digital proportional integtral adjustors, the output characteristic of the power source is controlled with the united feedback of current and voltage, and the feed wire speed is adjusted with double feedbacks of the arc voltage and the armature voltage, so that the welding parameters are accurately executed. The wire drawing or striking ignition modes are selected automatically according to the wire being touched work piece or not. The current decaying method is applied for filling the arc crater in the end of a welding process. A man-machine interface is developed with liquid crystal display to setup, display, memory, and manage the system variables, technological parameters and dynamic welding data by which the operating capability of the welder is enlarged.