The volume fraction and stability of retained austenite play an important role in the performance of low carbon steels, while the C and Mn elements have a stabilizing effect on the thermal stability and mechanical stability of retained austenite. Therefore, the C and Mn elementals partitioning was promoted by intercritical annealing. As a result, the mechanical properties of the low carbon steels are improved. The microstructure of quenching and partitioning bainitic steels and retained austenite characteristics were studied by means of SEM, TEM and XRD. The partitioning and content of C and Mn elements in retained austenite at different locations were characterized by EPMA, EBSD and nanoindentation. The effect of C and Mn elements on the stability of retained austenite at different locations and phase change law of retained austenite were investigated by combining the tensile stress-strain curves under the treatment of intercritical annealing (partial austenitizing)-quenching and partitioning in the bainitic region process (IQ&PB). In the process of tensile deformation, the transformation induced plasticity (TRIP) effect occurs, the volume of retained austenite decreases, the transformation takes place preferentially in the ferrite grain boundary, and finally occurs between the bainite laths. C and Mn elements have a stabilizing effect on the retained austenite, which make retained austenite is not prone to phase change. The stress at the tensile fracture is concentrated, and the retained austenite is completely transformed into martensite. The volume fraction of retained austenite is 3.12% and 5.03% at 2 mm and 4 mm distances away from the fracture. Film-like retained austenite is more stable than blocky retained austenite, and the retained austenite of the <111>_γ crystal orientation is unstable and easily transforms into martensite.