Abstract: The finite differential method was applied to calculating the temperature field and temperature curve of the cooling process of strip. Based on the experimental TTT curve, the CCT curve was deduced from Scheil's rule and Avrami equation. Then the temperature field and the phase transformation process were coupled to predict the ferrite grain distribution on the cross section of the strip. With the microstructure-property models the mechanical property distribution on the cross section, e.g. yield/tension strength, was calculated. The UFC (ultra fast cooling) technology and stepped cooling mode were applied to producing DP (dual phase) steels with low cost and good quality on site. The produced DP steels showed the low yield ratio, the tensile strength of 700 MPa and the ferrite grain size of 5~6 μm. This design process, adapting the cooling route based on the simulation results of the microstructure distribution, can decrease the production cost and increase the production efficiency.