Crystallization kinetics of undercooled Fe-B hypereutectic alloy was researched using differential scanning calorimetry (DSC) technique. With the combination of melt-fluxing and high pure argon gas to purify and protect the melts, high undercooling up to 410 K was obtained successfully. The comparison of time dependent transformation fraction at different undercoolings has shown that the crystallization rate increased firstly with increasing Delta T until 354 K and then, the crystallization process was retarded with the further increase of Delta T. Applying quantitative thermodynamic calculation, the evolution of the nucleation and growth rates as a function of temperature was described. On this basis, the temperature-time-transformation (TTT) curve was thus constructed, which gives a reasonable explanation of the observed experimental results. (C) 2011 Elsevier B.V. All rights reserved.