The structural, electronic and magnetic properties of a 9-layer symmetrical FeMoO terminated (001)-oriented slab of double perovskite Sr2FeMoO6 have been studied by using the first-principle projector augmented wave potential within the generalized gradient approximation taking into account the on-site Coulomb repulsive (U = 2.0 eV for Fe and 1.0 eV for Mo). An outward relaxation is observed for each layer of the first four layers and the accompanying layer's rumpling has a decreasing trend from layer 1 to layer 4. Along Fe-O-Mo-O-Fe or Mo-O-Fe-O-Mo chain, the oxygen atom is closer to the adjacent Mo atom than to the adjacent Fe atom. The half-metallic nature ensures the symmetrical FeMoO terminated (001)-oriented slab of double perovskite Sr2FeMoO6 to be a potential application in spintronic devices. The Jahn-Teller structural distortions and the outward relaxations lead to the differences between p(z) state and similar p(x) and p(y) states, between d(xy) state and similar d(yz) and d(x), states as well as between d(z)(2) and d(x2-y2). The reduction in the restrictions from the reduction in the number of the near neighbors, especially the vanishing of the nearest neighbor oxygen atom just above the transition-metal (TM) atoms on the first layer makes not only the remaining axial TM-O distances slightly shorter than the four equatorial TM-O distances but also shifts toward higher energy region the occupied up-spin and down-spin states with respect to the cases of the TM atoms on the third and fifth layers. (C) 2012 Elsevier B.V. All rights reserved.