Abstract: High strength steel is widely used in automobile, construction machinery and other fields, which requires both high strength and high toughness. The volume fraction of residual austenite in martensite high strength steel was regulated by quenching and partitioning process, and the transformation induced plasticity effect of residual austenite was introduced to obtain the high strength and toughness. Scanning electron microscope(SEM), X-ray diffractometer(XRD) and transmission electron microscope(TEM) were used to analyse the microstructure, mechanical properties and residual austenite content of the steel, and the mechanical properties of the test steel were tested by universal tensile testing machine. The results show that the microstructure of the experimental steel after quenching and partitioning at 350 ℃ for 60 s-3600 s is mainly composed of lath martensite, massive martensite and residual austenite, and the residual austenite is mainly distributed between the martensite lath in the form of bulk or thin film, and the width is about 100 nm. With the increase of the partitioning time, the residual austenite content first increases and then decreases. The highest volume fraction of residual austenite of the experimental steel is 19.7% when the partitioning time is 600 s, martensitic transformation is induced during the tensile process, and the best strong plasticity is obtained with the yield strength of 958 MPa, the tensile strength of 1482 MPa and the maximum elongation of 15.5%.