The phase equilibria of Co-V binary system were experimentally investigated, and the magnetically induced phase separation in the fcc phase was observed in a Co/V diffusion couple. Based on previous research and present work, a thermodynamic reassessment in the Co-V binary system was carried out by means of the CALPHAD method. The calculated results are consistent with the experimental data. The metastable miscibility gap of the hcp phase in the Co-V binary system was thermodynamically calculated. According to the calculation, the Co-V thin films with three concentrations were designed and deposited by magnetron sputtering. The transmission electron microscope (TEM) results prove that the metastable phase separation in the hcp phase exists in the Co-V system. The determined magnetic properties of the thin films reveal that the values of coercivity and remanence ratio are function of V content. (C) 2015 Published by Elsevier B.V.