The incipient melting process of a B bearing third generation single crystal superalloy was investigated by Thermol-Calc software. The simulation data was obtained by EPMA. The results show that the incipient melting phase was M2B and the incipient melting temperature was 1265 ℃, which is significantly lower than the melting temperature of eutectic (1352 ℃) obtained by DSC. The dissolution of γ/γ′ eutectics was studied by SEM. It was indicated that more time and higher temperature were necessary to dissolve the coarsen γ′ in eutectics than mosaic like eutectics and fan like eutectics. The sharp of incipient melting region was round. Homogenous nucleation could be found in incipient melting region due to the fast cooling rate of air cooling. The resolidification structure owned mosaic like eutectics and fan like eutectics which were dissolved in the early stage of solution heat treatment.