When Fe-15at%Si-13at%V alloy is aged at 1473 K for 7.2 ks, D0(3) (ordered b.c.c.) particles appear in the A2 (disordered b.c.c.) matrix. The D0(3) particles are cuboidal due to the elastic energies that arise from the lattice mismatch between the D0(3) precipitate and the A2 matrix phases. When the two-phase microstructure is aged at 923 K, very fine A2 particles precipitate in the cuboidal D0(3) particles that act as the matrix of the precipitation. The A2 precipitation is due to that the boundary between A2 + D0(3) and D0(3) at 923 K expands more widely to the D0(3) side than at 1473 K. In the course of further ageing at 923 K, the A2 particles coarsen to become plates in the D0(3) particles, which is also a result of elastic energies. While further ageing at 923 K, the A2 plates elongate along {100} to reach the A2 matrix surrounding the D0(3) particles, which results in the split of D0(3) particles. Such a split phenomenon brings the refinement or at least the decelerated coarsening of D0(3) precipitate in elastically constrained A2/D0(3) system of Fe-Si-V alloy.