First-principles calculations are attempted for phase stability, phase equilibria and microstructural evolution process of Anti Phase Boundary associated with ordering reactions in Fe-Ni, -Pd and -Pt binary alloy systems. Theoretical tools employed are 1. FLAPW electronic structure calculations for the total energies of selected ordered compounds, 2. Cluster Variation Method for deriving a free energy and 3. Phase Field Method to calculate microstructural evolution process. In order to derive effective cluster interaction energies, Cluster Expansion Method is also employed. The new aspect of the present calculation is CVM free energy is incorporated in the Phase Field model as a bulk chemical free energy density term. Hence, the atomistic and microstructural kinetics are simultaneously investigated. The main focus of the present study is placed on the disorder-L10 transition. It is revealed that the nearest neighbor pair interaction energy is dominant for all the three systems, which is a characteristic feature of a metallic alloy system. Calculated transition temperatures for Fe-Pd and -Pt are in good agreement with experimental values. For Fe-Ni system, it is found that L10 ordered phase is a stable phase although it has been missing in the conventional phase diagram. The congruent composition of Fe-Pd system is not reproduced and this may be attributed to the magnetic interactions. The coarse graining operation is performed and gradient energy coefficients are derived for Long Range and Short Range Order parameters. Unlike the conventional Phase Field Method, these gradient energy coefficients depend both on the temperature and ordered parameters. Microstructural evolution of Anti Phase Boundary associated with disorder-L10 transition is predicted from the first-priciples.