The area of glass formation in NaPO3–LiF–(0.4AlF3 – 0.6CaF2) system was determined. The glasses were synthesized using standard melt-quenching techniques. The concentration dependencies of the glass transition temperature, refractive index, density, molar volume, microhardness, and crystallization products were obtained. In (NaPO3)100-x–(LiF)x glass the linear decrease of noted parameters was observed. The LiF additives to the phosphate network caused the formation of a "friable" glass network. In (NaPO3)100-x –(0.4AlF3 – 0.6CaF2)x system the concentration dependencies were more complex due to the formation of a mixed fluorophosphate network. It was assumed that the structural groups changed from metaphosphate (PO3−)n in the initial composition to the combinations of P(O,F)4+[MeF6]+[MeF4] in the final stage. The microhardness values (>360 kg/mm2) of NaPO3– (0.4AlF3 – 0.6CaF2) glasses with high fluoride content were comparable to lead silicate glasses, which indicates the possibility of their practical application in optical instrumentation and devices.