The TMCP and bake hardening experiments were carried out for the test steel，the microstructure analyses，mechanical properties and bake hardenability test were carried out by using SEM, TEM and tensile test machine. The results show that small volume fraction of bainite microstructure increased will improve BH value in the microstructure of F+P(little). compared with the microstructure that consists of ferrite mainly，which consists of bainite mainly has a higher BH value. The microstructure that consists of ferrite mainly shows the trendy of BH that increased first and then decreased, along with pre-strain increased. The microstructure that consists of bainite, under the condition of higher pre-strain, with the pre-strain increased, the BH value shows the trendy of increasing. While the BHT value is increasing monotonously.