The Tuning Method for a controller suggested by Yunwana and Seborg (1982) could not be applied to a system with time delay due to phase error by Pade' Approximiation. In this paper theoretically analyzes the phase error to find that phase error by Pade' Approximation and Time Delay are the major causes and suggests a novel optimal tuning method to solve those problems through configuration of regulators by means of bilinear transformation based on a previous study Suh (1984).