The ultrafine grain with the effective grain size of 1.10 μm was fabricated by intercritical deformation on low-carbon microalloyed steel, which was finer than the deformation induced ferrite transformation (DIFT) at 1.55μm.Duringintercriticaldeformation,theDIFTprocesswasenhanced,showingacolonydistributionoftherefined grains. Meanwhile, the continuous dynamic recrystallization of pro-eutectoid ferrite was developed by both the subgrains progressively trapping dislocationsand theserratedboundary pinchingofftheelongatedgrains. These processes were directly observed through the grain average misorientation maps of electron back-scattered diffraction and confirmed by transmission electron microscopy micrographs.