Ash deposition has a major impact on safe and economic operation of coal-fired boiler.A new method for ash melting thermo-analysis based on X-ray diffraction mineral quantitative analysis was developed;the classical thermal analysis theory was used to describe the dynamic behavior of ash melting.The low-temperature ash melting process curve was acquired.Compared with the conventional method of ash fusibility,the new method of ash melting characteristic curve reflects the ash melting dynamic better.The ash melting characteristic curve reveals the multi-stage reaction process of minerals melting,explains the gradual increase of mineral melting process in theory.