A rational flexural strength design method, which fulfills the assumption of complete composite action, was developed for steel reinforced concrete (SRC) beam sections. The proposed design method, which is named as MMC method, is fairly simple and accurate. Therefore, sections designed according to MMC method are more economical then those designed according to the strength superposition method. For those sections designed according to MMC Method, a minimum ductility ratio of 2, at the spalling of the cover concrete, can be reached. With the limitation of hoop spacing no greater than 8 times the diameter of main reinforcing bar, the designed sections are able to reach an ultimate ductility ratio of at least 9. Which is consider adequate for ductility design of earthquake-resistant structures. In addition, empirical formulas were established to evaluate the curvature ductility ratio of SRC sections.