Metal-metaphosphate glasses have been investigated by far infrared spectroscopy to describe of the glass structure.The broad absorption band assigned to cation vibration in its oxygen cage appeared as envelop of the optical phonon spectrum of the crystalline form the material.The deconvolution of far infrared asymmetric absorption profile indicates alkali cations occupy two distinct network environments.For (75-x)M2PO3·xM2 PO3· 25Al(PO3)3, the vibration of cations shift with x indicated the local geometry of cations are affected by the introduction of the second cation into glass structure.