Quenching and partitioning (Q&P) is one of the most promising heat treatment processes proposed by Speer, et al., is very effective to produce martensite and high fraction of retained austenite microstructure in steels that could lead to high strength and ductility. Based on the knowledge on physical metallurgical aspects and by comparing the literatures on Q&P process, four alloy elements of C, Mn, Si, and Al were chosen and the isopleths were plotted by varying each chosen alloy contents by using Thermo-Calc software. From the results of above calculations three new suitable Q&P steel compositions were identified and melted. Different Q&P heat treatment were done on the designed steels by varying quenching and partitioning temperature and time. Based on the obtained final volume fraction of retained austenite and comparing the tensile properties, Q&P process parameters were optimized for further analysis. The detailed microstructural characterization was done by using synchrotron high energy X-ray diffraction (HEXRD), electron back scattered diffraction (EBSD) and transmission electron microscope (TEM). The carbon distribution between the phases was measured with the atom probe tomography (APT). The results were compared with the carbon diffusion profile between martensite and austenite simulated by using the DICTRA coupled with Thermo-Calc software. The carbon partitioning mechanism with respect to change in partitioning temperature and time was postulated for the Q&P steels.