Abstract: The control system of a three-phase AC regulator consisting of two monolithic microprocessor 8749s,and using parallel operation mode is presented in this paper. It ensures the ability and speed of treatment in a large range dynamic process. In the meantime it can do auto-checking and auto-treating for innormal situation in the line and load or inside of the power system. Good results have been obtained through tests of a 15 K VA regulator model.