Abstract: Based on low carbon+Nb, V and Ti microalloying, the microstructure of Q500qE with a small amount of Cr and Ni under different controlled rolling and cooling processes and the effect of different microstructure on yield-strength ratio were studied. The results show that when the steel is initial cooled at 725 ℃ and finally cooled to 500 ℃ at 15℃/s, the multiphase structures of proeutectoid ferrite, acicular ferrite and lath bainite are generated in the steel, which have lower yield-strength ratio.