Abstract: The effect of carbon content on the morphology of proeutectoid ferrite grains in Fe-C alloys annealed in high magnetic field was investigated, especially in high-purity Fe-0.12C, Fe-0.36C, Fe-0.52C and Fe-0.76C alloys. The results showed that the grain size of the proeutectoid ferrite gradually decreases with increasing carbon content and the trend to elongating the grains in the magnetic field direction to form chain-like arrangement becomes weaker. This phenomenon is not only attributed to the different carbon contents of the Fe-C alloys, but also closely related to the formation process and evolution mechanism of the proeutectoid ferrite grains. Consequently, a magnetic dipole model is proposed applicable to the early stage of proeutectoid ferrite transformation in low carbon Fe-C alloys or in case the distance between proeutectoid ferrite nucleus is relatively long in the Fe-C alloys in which the carbon content approaches the eutectoid composition.