In the present study, a new fire resistant steel for construction was developed, which is a low carbon Mn-Mo steel microalloyed with Nb and Ti. The mechanical properties of the alloy were studied by tensile and impact testing. The effects of parameters in controlled rolling and controlled cooling process on the mechanical properties and the microstructures of the steel were investigated. It is found that the strength of the steel increased as the reheating temperature increased and finish rolling temperature decreased. The results also showed that the finish cooling temperature had a very important effect on the mechanical properties. As the finish cooling temperature decreased, the strength of the steel increased obviously. The microstructures were observed by OM and TEM. The relationship between the mechanical properties and the microstructures of the steel was discussed and the strengthening mechanisms of the studied alloy were also analyzed. In the paper, the rolling schedules for industrial production of the steel were suggested.