The microstructures and mechanical properties of bainite/martensite (B/M) multiphase steels treated with high-temperature duration and continuous cooling were studied. The steels treated at 623 K and cooling rate of 0.5 K/s exhibited a multiphase microstructure containing carbide-free bainite, martensite and film-like retained austenite. Observation in-situ showed the carbide-free bainite was nucleated and dispersed intragranularly with excellent tensile strength of 1920 MPa and total elongation of 14.6%.