Abstarct: Steam generator is a major power plant component. The heat produced by the fission reaction is swept away by the reactor coolant which is circulated through the primary circuit into the steam generator , it delivers its energy through the U-tube pipes to the water in the steam generator and produces steam. The problem has been of great concern for many years as the steam generator is a highly nonlinear and complex system, showing inverse response dynamics especially at low operating power levels. the inverse thermal hydraulic behavior (non-minimum phase characteristic) due to swell and shrink effects especially at low operating power levels. If the steam generator level goes too low, there is not adequate water in the steam generator to be converted to steam, and remove the heat. If the steam generator level goes too high, there is a potential of water droplet carry-over to the turbine, which could damage the turbine blades. Therefore, the level of the steam generator need to be maintained between the required limits. In this thesis, is to design, analyze a water level controller for U-tube steam generators using PI, fuzzy controller. To attain a good performance in all powers, Computer simulations show that the proposed controller improves transient response of steam generator water level through the entire range of operation and demonstrate its superiority to existing controllers