The effect of Nb addition in rapid-quenched (Nd,Dy)11.5Fe82.4-nNbnB6.1 (n=0,0.5,1,1.5,2) permanent magnets on the magnetic properties, temperature characteristics and microstructure has been investigated. It is found that Hcj increases with increasing Nb content and the irreversible loss of magnetic flux decreases. Nb addition results in smaller grains and more homogeneous and regular grain structure. It is considered that Nb addition may enhance exchange coupling pining field and reduce internal stray magnetic field. As a result, the irreversible loss of magnetic flux decreases notably and the magnetic properties at higher temperature are improved.