An interest of chalcogenide glass has been increased because of their use in preparing optical lenses in range of 3-12 μm.With recent advance in less costly uncooled detector technology, moldable lens using chalcogenide glass has drawn a great deal of attention. In this study, amorphous Ge-Sb-Se chalcogenide was prepared by a standard melt-quenching technique. Melted chalcogenide glass for moldable lens should have unique thermal and mechanic properties in order to be applied to molding process. Specifically, the Ge:Sb ratio were controlled in order to find out the most stable glass forming area. Thus, the optical, thermal and thermomechanical properties to find out the specific composition were characterized by FT-IR spectroscopy, Differential Scanning Calorimeter and Thermo Mechanical Analysis, respectively. The moldability of chalcogenide glass was characterized through the surface condition of glass samples. Finally, the preferential Ge:Sb ratio in Ge-Sb-Se based chalcogenide glass system was selected to fabricate moldable lenses.