We first applied Ca-43 3QMAS NMR spectroscopy for Ca-43-enriched model slags. Local environments of Ca2+ ions in slow- and rapid-quench model slags were found to be different each other. The slow-quench slag has well-defined CaO8 polyhedra in a crystalline form, although the rapid-quench slag is considered to have CaO6 octahedral species as a main component.