Based on the density functional theory (DFT), the plane-wave pseudo-potential method was used to calculate structural stabilities, elastic properties and electronic structures of Fe3Si and Fe3Si-X (X=Ni, Co, Cr) compounds. The stability of the solid solution alloy increases with the addition of Ni or Cr, especially Fe3Si-Ni, and the stability of the solid solution alloy decreases with the addition of Co. The calculated elastic constants show that addition of Ni or Cr could enhance the plasticity and ductility, and Co could improve the hardness of compounds. Fe3Si-Ni has a better plasticity, but Fe3Si-Co has the best high temperature stability. Calculation of the density of states and Mulliken electronic populations shows that the reason why Fe3Si-Ni has the highest structural stability and optimal plasticity is attributed to its Fermi level close to the bottom of the pseudogap. And Fe3Si-Ni has the biggest Mulliken population with the metallic bonding of the alloying system increasing.