Major issue of modern power system having complex power structure, it is necessary for Thermal Generating Unit (TGU) to continuous supplying an electric power with the increasing demand. Owing to this Automatic Generation Control (AGC) play a key role for maintaining the frequency oscillation and tie-line power due to unpredictable load changes. This paper help to solve the settling time issue of load frequency and tie-line power for multi area (Five area) AGC interconnected TGU Reheat and Non-Reheat system using different controllers like GA (Using Tuning of PID) controller, Fuzzy controller and PID controller. For better results the combined response of frequency and tieline deviation has been obtained separately for multi areas reheat and non-reheat T.G.U system and the comparative Tables of the entire controller’s response is taking place separately. The results obtain from the combined response and comparative table, shows that GA controller gives the better dynamic performance due to settle down frequency and tie-line power deviation in less time and satisfy the automatic generation control requirements.