Since many power plant boilers in operation have already reached 150,000 to 350,000 hours of operating time, determining the amount of remaining life is becoming increasingly important to prevent the problem of boiler tube leakage due to long-term operation. It has so far been difficult, however, to logically determine the appropriate time of inspection, resulting in great cost and effort. Based on a statistical analysis of inspections over more than 30 years, with data classified by boiler specifications such as operational age, type of combustion, design pressure and design temperature, etc., Mitsubishi Heavy Industries, Ltd. (MHI) has created a boiler life estimation system intended to direct the determination of detailed inspection times by predicting the tube creep remaining life and the remaining life of tube thickness reduced by corrosion. This paper introduces an outline of the system.