A systematic design methodology for discrete control systems is proposed, which is based on Galois field and Gröbner basis. The controller can be automatically designed using a model of the controlled plant. The controlled plant is represented on Galois field. Then the inverse function of the plant is derived using Gröber basis so that the input variables are explicitly obtained as the function of the state variable and reference variable. An illustrative example of a material handling system is shown. The proposed method will realize cost reduction in software development and an improvement of reliability and safety of the PLC based systems.