Abstract: The 14mm-thick Nb-Ti microalloyed hot-rolled multiphase steel plate was developed by two-stage rolling and subsequent three-step cooling, then it was characterized by optical microscopy, SEM, TEM, XRD, EBSD (electron back-scattered diffraction) and other tests to investigate its microstructure and mechanical properties. The results indicated that the microstructure of the steel specimen is composed of ferrite, bainite and small amount of martensite, and that the mean yield strength, tensile strength and percentage elongation are 518MPa, 616MPa and 41%, respectively. The existence of lots of big-angle ferrite grain boundaries, near-equiaxial ferrite grains and small bainitic beams significantly improves the ductility. The refinement of ferrite grains and bainitic structures, fine (Nb, Ti)C particles and the dislocations in ferrite and lath bainite increase the strength.