Bake hardening steels offer a suitable response to automotive bodywork requirements. By providing an excellent formability and dent resistance combination, they enhance vehicle weight reduction and aesthetics. The composition and processing of these steels are designed to promote a significant increase in yield strength during low-temperature heat treatment, particularly paint curing. In the current research, a new constitutive equation was presented to model the bake hardening effect on flow behavior of dual phase DP500 steel during tensile test. Experimental procedures such as nano-indentation and theoretical models were used to identify the mechanical properties of the constituent phases (ferrite, martensite and tempered martensite). Representative volume element (RVE) of microstructure of the studied steel was regarded, material properties were assigned to constituent phases and tensile test was simulated using Abaqus. The results showed that the flow curve of the studied DP steel after baking can be predicted properly using the developed model.