Nanocomposite rare-earth magnet of Nd2Fe14B/alpha-Fe has attracted considerable interest because of its very high potential magnetic performance resulting from significant ferromagnetic exchange coupling between the hard and soft magnetic grains. In the present paper, a series of nanocomposite rare-earth magnets of Nd2Fe14B/alpha-Fe were prepared by melt-spun method. The nominal compositions were Nd9Fe85B6, Nd9Fe84.5B6Nb0.5, Nd(10.5)sFe(83) B6Nb0.5, Nd15Fe76.5B8Nb0.5 containing different content of alpha-Fe. The effects of the composition, nanophase constitution and grain size on the properties of nanocomposite Nd2Fe14B/alpha-Fe were studied. The results show that the grain refinement due to adding Nb has led to strong exchange coupling effect between the grains of hard and soft magnetic phases. By the optimization of the processing conditions, the relative high performance: J(r) = 11.27 kGs, H-ci = 8.99 kOe, and (BH)(max) = 18.31 MGOe is obtained in the Nd10.5Fe83 B6Nb0.5 alloy. The observation of Atomic Force Microscope (AFM) and Magnetic Force Microscopy (MFM) shows that the size of the magnetic domain in the alloys is about 350 mu, much bigger than the mean grain size. The scale of this contrast corresponds to that of interaction domains, which is related to the exchange coupling effect and consistent with earlier studies. MFM is thus a useful technique for studying the interaction domain structure.