Abstract: The eff ect of heat treatment process on the yield strength ratio of 690 MPa grade high strength steel was studied. The microstrueture of the corresponding process was analyzed by metallographic micrescope. The results show that,using 860℃×50 min quenching and 610 ℃×50 min tempering process, the mechanical properties of the steel plate meet the standard GB/T 16270-2009 requirements for 690 MPa grade high strength steel. At the same time, the yield strength ratio decreases to 0.92, the matrix microstructure is tempered sorbite+needle flake ferrite. After "critical temperature quenching and high temperature short time tempering" process, the yield strength ratio of 690 MPa grade high stre ngth steel can be greatly reduced, while maintaining good strength, not reducing or slightly reducing the toughness and plasticity.