The Increasing complexity of Geothermal Power Plants (GPPs) installations and operations, along with growing public awareness to ensure higher levels of reliability, has put great pressure on the designers and operators to find innovative solutions to ensure reliability as well as economically viable operation. Critical Analysis becomes a major task for analyzing appropriate maintenance strategies for every equipment to increase reliability, especially in Geothermal Steam Turbine System. FMEA is one of the tools to prioritize equipment based on their failure modes. FMEA is a calculation from severity, occurrence, and detection. The results of this factor are RPN (Risk Priority Number). The use of RPN is to compare the criticality risk among Geothermal Steam Turbine System. However, the combination of severity, occurrence, and detection may yield the exact same RPN value despite significant differences in their risk implications. This problem occurs because the relative importance of severity, occurrence, and detection is not taken into account. The use of fuzzy logic approach would make the relative importance of severity, occurrence, and detection is considered. The fuzzy logic approach would make the results becomes more comprehensive rather than conventional FMEA methods. This method would be used for prioritizing Geothermal Steam Turbine System.