Abstract: The microstructure of hot-rolled dual-phase steel was studied by scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The volume fraction of each phase in the dual-phase steel was determined by Image-Pro Plus software. A microstructure-based model was deduced for the stress-strain relationship of the dual-phase steel according to the mixing rule of multiphase materials and the Swift equation. Then the model was verified by the strain-stress curves of DP590 and DP780 steels obtained from uniaxial tensile testing. The results show that the model expounds the relationship between the microstructural parameters and macroscopic mechanical properties,and it is able to accurately describe the deformation behavior of materials and well predict the tensile curve of hot rolled dual-phase steel.