Influence of thermo-mechanical controlled processing(TMCP),including two-stage rolling with laminar cooling,air cooling and ultra-fast cooling,on the microstructure and mechanical properties of three kinds of Nb-microalloeyed steels was investigated by hot-rolling experiment.Effect of chemistry compositions and microstructure on mechanical properties and the relationship between the multiphase microstructure’ s formation with TMCP were analyzed.The results showed that the mixed microstructure containing ferrite,bainite,martensite and a small amount of retained austenite can be obtained by thermo-mechanical controlled processing.Size, quantity and distribution of the constituents(ferrite grain,bainite packet and M-A islands) significantly affect the mechanical properties of three kinds of Nb-microalloyed steels.Under the condition of similar TMCP parameters, there is a gradually decreasing tendency in tensile strength from high silicon Nb steel,high silicon Nb-Ti steel to low silicon Nb-Ti steel,and an opposite tendency in total elongation and product of tensile strength and ductility. Total elongation and product of tensile strength and ductility reach the maximum values(41%and 25256 MPa% respectively) for low silicon Nb-Ti steel. Influence of thermo-mechanical controlled processing (TMCP), including two-stage rolling with laminar cooling, air cooling and ultra-fast cooling, on the microstructure and mechanical properties of three kinds of Nb-microalloeyed steels was investigated by hot-rolling experiment. Effect of chemistry compositions and microstructure on mechanical properties and the relationship between the multiphase microstructure ’s formation with TMCP were analyzed. The results showed that the mixed microstructure containing ferrite, bainite, martensite and a small amount of took austenite can be obtained by thermo- mechanical controlled processing. Size, quantity and distribution of the constituents (ferrite grain, bainite packet and MA islands) significantly affect the mechanical properties of three kinds of Nb-microalloyed steels. Under the conditions similar to TMCP parameters, there is a decreasing tendency of in tensile strength from high silicon Nb steel, high silicon Nb-Ti steel to low silicon Nb -Ti steel, and an opposite tendency in total elongation and product of tensile strength and ductility. Total elongation and product of tensile strength and ductility reach the maximum values ​​(41% and 25256 MPa% respectively) for low silicon Nb-Ti steel.