The oxidative dehydrogenation of cyclohexane was studied over Mg-V-O catalysts with different Mg/V atomic ratios. Catalysts were prepared via citric acid complexation and characterized by N-2-adsorption, XRD, FT-IR, Raman spectroscopy, NH3-TPD and H-2-TPR techniques. Among the pure magnesium vanadates, Mg-3(VO4)(2) has the isolated active sites, weakly basic surface and lower reducibility of the metal cations, and could be recognized as the catalytic active phase. Furthermore, a series of mechanically mixed catalysts were studied in the reaction in attempting to investigate the synergetic effect. The finding revealed synergetic effects in the conversion, in the yield, and in the selectivity were observed in Mg-3(VO4)(2) mixing with a suitable amount of MgO and Mg2V2O7 due to a solid solution of MgO in the Mg-3(VO4)(2) phase and the remote control mechanism, respectively. Among the biphasic catalysts, (7/4)MgVO catalyst exhibited a better catalytic performance, on which a cyclohexene selectivity of 45.7% at cyclohexane conversion of 13.9% was obtained.