An Ejector enhances system efficiency, are easily operated, have a mechanically simple structure, and do not require a power supply. Because of these advantages, the ejector has been applied to a variety of industrial fields such as refrigerators, power plants and oil plants. In this work, an ejector was used to safely recycle anode tail gas in a 75-kW Molten Carbonate Fuel Cell (MCFC) system at KEPCO Research Institute. In this system, the ejector is placed at mixing point between the anode tail gas and the cathode tail gas or the fresh air. Commercial ejectors are not designed for the actual operating conditions for our fuel cell system. A new ejector was therefore designed for use beyond conventional operating limits. In the first place, a few sample ejectors were manufacured and the entrainment ratio was measured at a dummy stack. Through this experiment, the optimum ejector was chosen. The 75-kW MCFC system equipped with this optimum ejector was operated successfully.