Nonempirical study of the site preference occupation for Ni and V substituting in Fe3Al has been carried out in the framework of the coherent potential approximation. Obtained values of total energies show in a full agreement with experiments that Ni atoms in the equilibrium configuration occupy the iron sub-lattice for alloying with 5 at % of Ni in the Fe3Al-based alloy. Calculations of alloys with the V-doped iron aluminide in the DO3 phase show differences in bonding and site occupation preferences in comparison with Ni doping. V atoms occupy aluminum sublattice.