Ab-initio study using the density-functional theory (DFT) method to investigate the role of MgO, a basic material to oxidative dehydrogenation of C3H8 and n-C4H10 using V2O5 catalyst. The detailed calculations suggest that V2O5/MgO instead of compound Mg-3(VO4)(2) can be used for ODH of both alkanes but V2O5 supported on MgO may not be the most suitable catalyst for the ODH of n-C4H10. And when preparing the catalyst for ODH of n-C4H10 it should be avoided creating Mg-3(VO4)(2), a low catalytic activity. (C) 2011 Elsevier B.V. All rights reserved.