Though thermodynamic calculation is mainly applied to understanding materials states close to equilibrium, the computational thermodynamics, so called the calphad method, has also been extensively employed to exploiting new class of materials. In the development of the advanced high strength steels for automotive applications, despite that processing routes are in a highly non-equilibrium situation, thermodynamic calculations combined with high quality database give valuable information such as range of phase stability, stable/metastable phase fraction with composition in each heat treatment stage and oxide formation in selective oxidation environment. Taken the case of the low-alloyed TRIP steel as an example, some calculated results are shown and advantages and limitations of the calphad approach in finding the optimal alloy chemistry and processing parameters for a given application are discussed.