To develop 590MPa grade low yield ratio steel for high-rise buildings, the new generation TMCP based on ultra fast cooling (UFC) technology was proposed. Then effects of UFC final temperature on microstructure and mechanical properties were investigated. The results show that the control of composite phases is important to obtain high strength, low yield ratio and high work hardening exponent. When UFC final temperature is 521°C, 22.5% (volume fraction) M-A phases are distributed in bainite ferrite matrix, and the excellent overall properties can be obtained, i.e., the yield strength is 570MPa, tensile strength 760MPa, yield ratio 0.75 and percentage elongation 22% with the Charpy impact energy 284J at -40°C. All these indexes can meet the requirements of relevant standards.