Abstract: Due to the melting temperature of Dananhu No.2 Mine coal could not accurately predict its slagging characteristics, the content of metal elements were obtained with microwave digestion technology for raw coal and its ash prepared with GB/T 212—2008 Proximate Analysis of Coal.The results reveal that in the process of preparing ash by using GB/T 212—2008 standard, the main metal elements in the coal escape to various degrees. Metal oxide escape rate can explain the metal elements escape characteristics, the escape rate of K2O and Al2O3 with high melting points are 47.92% and 42.48%, the escape rate of CaO with relatively low melting point is 36.50%, and the escape rate of Fe2O3 is the smallest, but also reach to 10.60%. The ash melting point is affected enormously by the escape of metal elements, which offends against the actual of coal slagging characteristic.The escape of metal elements enormously influences the ash melting point, resulting in a 70 ℃ difference between the softening temperature of 1 200 ℃ of the ash made under 500 ℃ and that of 1 270 ℃ of the ash made under 815 ℃ by the standard method. Therefore, compared to ash melting temperature, ash composition comprehensive prediction index can be more exactly described the practical slagging characteristics of Dananhu No.2 Mine coal.