The freckle formation and their phase characterizatics in freckle areas were investigated by means of microstructure analysis approaches and a thermodynamic equilibrium phase calculation method in an Inconel 625 alloy.These results show that in freckle areas a large number of M6C, MC, Laves and δ phases precipitate in grain boundaries even within grain due to the enrichment and segregation of Mo and Nb during solidification, which results in almost of these freckle areas covered by these complex precipitated phases and induces small grains in freckle areas.Equilibrium phase and liquid segregation calculation can give a reasonable interpretation of the freckle feature for this alloy.