Abstract: The quantitative phase analysis of Nd₁₅ Fe_85-x(x=0, 2, 4, 8, 11) alloys have been studied by the Mössbauer effect. The effect of boron content on the phase construction which influences the magnetic properties of Nd-Fe-B alloys is discussed. It is found that the quantity of the tetragonal phase increases (x<8) with increase of the boron content, reaches the maximum at x=8, and then decreases (x>8). In the Nd₁₅Fe₇₇B₈ phase, which has optimal magnetic properties, the relative quantities of the tetragonal phase, the B-rich phase and the Nd-rich phase are 84.6%, 4.6% and 10.8% respectively. The remanence of the alloys was estimated from the data of the quantity of the tetragonal phase and magnetic moment orientation degree. The calcalated results accord with those of the experiments.