The crystallization behaviours of nanocomposite made by a function of quenching rate (roller speed) were studied. The results showed that there was one step crystallization process for the alloy quenched at roller speed of 32 m/s, which could be shown as, Am (amorphouse) + α-Fe+Nd₂Fe₁₄B →α-Fe+Nd₂Fe₁₄B. For the alloy quenched at roller speed of 40 m/s, there was steps crystallization process taking place at different temperatures, which could be shown as, Am → α-Fe+Nd₂Fe₂₃B₃+Nd₂Fe₁₄B+Am'→α-Fe/Nd₂Fe₁₄B. The presence of transition phase (Nd₂Fe₂₃B₃ ) was harmful to get fine and uniform grain size during crystallization process. Uniform microstructures and high magnetic properties could be attained for the as-quenched alloy containing less amorphous phase and no presence of transition phase during annealing treatment. For the alloy prepared at roller speed of 32 m/s, the following properties were obtained, B_r=0.904 T, _iH_c=801kA/m,(BH)_max=122 kj/m³ and M_r/M_s= 0.6.