Abstract: Coal ash fusion temperature is important for large-scale gasifier/boiler designers and operators. There has been a big error for fusion temperature calculated by chemical composition of coal ash because the ash is composed of minerals actually, which has a strong impact on fusion temperature. A new calculation method, based on chemical composition and low temperature eutectics of minerals being considered, is proposed, according to 59 typical coal samples from the central and western regions in China. The most predictive values are not far from preciseness with a mean error lower than 5%, when the calculation is employed to 108 coal samples. Meanwhile, a roughly sufficient judgment to identify the ash fusion temperature greater than 1 500℃ is suggested by formula, which is 0.9≤SiO₂/A1₂O₃≤1.8 and SiO₂+A1₂O₃≥78% with accuracy of 92.2% among 167 coal samples.