Effects of Nb addition and annealing treatmen on magnetic properties and microstructure of（Nd0.4Pr0.6）9Fe76–xNbxB15（x = 0–4） ribbons were systematically investigated by means of vibrating sample magnetometer（VSM） and X-ray diffraction（XRD）. The extra phases with nonmagnetic（Nd,Pr）1.1Fe4B4phase and metastable compound（Nd,Pr）2Fe23B3 crystallized during quenching the Nb-free alloy. Moreover, the nonmagnetic（Nd,Pr）1.1Fe4B4phase does not diminish during the following annealing treatment. The addition of Nb to（Nd,Pr）–Fe–B alloy suppresses metastable（Nd,Pr）2Fe23B3 and nonmagnetic（Nd,Pr）1.1Fe4B4phases. The intrinsic coercivity increases from 397 kA m-1for the Nb-free sample to1,091 kA m-1for the 4 at% Nb-doped sample optimally annealed. The Nb-free sample has the magnetic properties with Js= 1.04 T, Jr= 0.66 T, and（BH）max= 43.5 kJ m-3By comparison, the magnetic properties of the 4 at% Nbdoped sample were 0.97 T, 0.68 T, and 65.7 kJ m-3respectively. The significant improvement of magnetic properties mainly originates from the finer grains of the ribbons by introducing Nb.
