Abstract: Through rolling simulation of 590L auto beam steel,microstructure and properties of the steel under different microalloying conditions are investigated.Research results show that microstructures of acicular ferrite and a small amount of bainite obtained from microalloying with Nb,V,Ti,and B can satisfy the strength and toughness requirements of 590L auto beam steel.According to the research results in the laboratory as well as production experience,trial production has been carried out and qualified 590L auto beam steel has been successfully developed through optimization of composition and process design.The microstructure and properties of the steel so produced can fully meet the users’ requirements.