A certain amount of retained austenite in the dual phase steel was obtained through a rational heat treatmentprocess,and the steel thus achieved a good combination of strength and plasticity.Then,the microstructure ofthe DP steel was investigated by means of the optical metallography,XRD and the electron back-scatter diffraction( EBSD),and the evolution rules of the retained austenite during the deformation were discussed.The results showthat ( 1) the retained austenite is fine and mainly granular,and most of it distributes uniformly at the boundaries offerrites and /or martensites with few in the ferrites; ( 2) the transformation of retained austenite mainly occurs at thedeformation extent of less than10%,and it is linearly related to strain at the deformation extent of more than 10%;and ( 3) in the EBSD observation,the retained austenite is not found in the fractured sample after tensile fracture.