The causes and mechanism of hygroscopicity of binary ultraphosphate glasses are difficult to study. This is due, in particular, to the formation of a thin layer of partially hydrolyzed glass with physisorbed water. 1H MAS NMR is more suitable than IRTF spectroscopy to investigate very hygroscopic glasses. In absence of atmospheric humidity, two distributions of OH residual groups are proposed. One of these distributions depends greatly of the induced disorder caused by the associated cation. In equilibrium at room temperature with atmospheric humidity we observed an increase of these second distribution and a new OH distribution corresponding to hydrogen bond with absorbed water.