Abstract: The present research of ultrafine grain steel is described,and the influences of ZrC particles on thermodynamic conditions,kinetic relation and ferrite grain refinement of deformation induced ferrite transformation (DIFT) in test steel containing ZrC particles during deformation of undercooled austenite are described.It is pointed out that the new methods of gathering deformation defects including adding second-phase particles are the key techniques under the condition of lack rolling force of existing equipment in China to obtain low carbon steel plate with ultrafine grains.Then, develop prospect of grain refinement during DIFT process in low carbon steels has been introduced.