Abstract: The Nb-contained microalloyed experimental steel was investigated via thermomechanical controlled processing (TMCP) including two-stage rolling with laminar cooling, air cooling and ultra-fast cooling over three different finish rolling temperature intervals. After such a TMCP, the microstructures containing ferrite, bainite, martensite and a bit of retained austenite were obtained. Then the effect of controlled rolling temperature interval on the microstructure and mechanical properties of experimental steel was analyzed. The results show that when controlled cooling parameters are similar to each other, tensile strength decreases but yield strength, percentage elongation and product of tensile strength and ductility all increase with the decreasing starting and final temperatures of finish rolling. With the cooling conditions during TMCP mentioned above, when the temperature interval during finish rolling is 850~800°C, yield strength, percentage elongation and product of tensile strength and ductility all come up to their maximum values, i.e. 513 MPa, 35% and 25235 MPa·%, respectively.