Abstract We have studied the demagnetization behavior for melt-spun nanocomposite Pr 8Fe 87B 5 ribbons in this paper. We have defined H ex which reflects the magnetic hardening of α-Fe and H irr which expresses the irreversible reversal of magnetic hard phase. It is found that magnetization behavior can be well described using H ex and H irr. A magnetic single-phase behavior is observed as H irr approximately equals to H ex. Remanence enhancement is not only determined by the intergrain exchange coupling but also dominated by the anisotropy of Pr 2Fe 14B phase. To achieve a high energy product (BH) max, the ideal microstructure is discussed. The magnetic reversal in the ribbons is mainly controlled by inhomogeneous pinning of nucleated type.