In order to know the microscopic mechanism of selective deposition of coal ash in the area nearby clean water wall and to provide some theoreticsl basis to solve the problem of complex slagging,the ultrasoft pseudo potential plane wave method was introduced based on the first principle to calculate the electric structure and thermodynamic properties of Al2O3,SiO2 and Fe2O3.The most stable structure was achieved and the electric structure and cell parameters of the three materials were calculated.Then the thermodynamic properties were derived and the temperature entropy product T*S,heat capacity cp,enthalpy H and Gibbs free energy G of the three minerals were obtained in the light of the metod of phonon spectra state density.Corresponding curves were fitted with the data acguired.