A large interconnected power system consists of large and small generating stations and all stations must have same frequency. Fuzzy-PID (Propositional-Integial Derivative) control method has been applied in this work for Automatic Generation Control (AGC) of multi-area power system with Generation Rate Constraints (GRC). The objective of providing an Automatic Generation Control (AGC) is to maintain the system frequency at nominal value and the power interchange between different areas at their scheduled values. The main requirement of an interconnected AGC is to ensure that the frequency of various bus voltages and currents are maintained at near specified nominal values, and tieline power flowing among the interconnected areas are maintained at specified levels, and total power requirement on the system as a whole is shared by individual generators economically in optimum fashion.The main work of AGC is to maintain constant system frequency. This method is used in the control system having three areas with steam turbine and one with hydro turbine tied together with power lines. The performance analysis of AGC using fuzzy-PID controller is presented in this paper.