Regenerative air heater at steam power plant (PLTU) is an air heater driven by a fan and gas into the boiler. The heat transfer process occurs because of the rotating element so that the heat energy of the combustion air is absorbed by the metal sheet on specially formed elements. The use of an air heater can increase the thermal efficiency of the unit by up to 10%.This means saving fuel usage of heat energy reused in water heater. Decrease of peforma air heater will reduce the performance of the unit so that it can give a loss impact for a plant. So to overcome it required proper maintenance to prevent the decrease of performance on the air heater. There are several maintenance parameters required to maintain the performance of the air heater. The maintenance parameters can be analyzed to get the performance of what things need to be optimized. This study aims to provide maintenance parameters that must be done to improve the return value of the air heater performance. Evaluation of air heater is done based on ASME PTC 4.3 to know the performance of air heater used in PLTU Suralaya with reference parameters to gas side efficiency and air heater leakage. The evaluation is based on working conditions when the maximum load and the calorific value of coal are assumed to be the same. Performance is evaluated within 6 consecutive months in comparison with the value of performance during commissioning.Then the performance decline will be analyzed with a fault tree analysis to determine the cause of decreasing the efficiency value of the gas side and increasing the leakage value. .