Abstract: The microstructures of hot rolled Ti-Mo-bearing low-carbon steel and its precipitation characterization of nano-sized carbides were studied by scanning electron microscopy and transmission electron microscopy. It is shown that precipitation strengthening due to nano-sized carbides is estimated to be approximately 291 MPa. The row spacing of interphase precipitation decreases with the drop of isothermal holding temperature. Though the row spacing of interphase precipitation in ferrite shows a relatively small scatter,it tends to be almost constant against distance from the center of ferrite transformed at different holding temperatures. The observed α/γ interfacial microstructure and interphase precipitation simulation by different theories indicate that this interphase precipitation has a close relationship with the formation of mobile ledges,and the row spacing of interphase precipitation is determined by factors such as ledge height,boundary diffusion coefficient,holding temperature,and ledge velocity.