By using first-principles electronic structure and transport calculations based upon the density functional theory, we have studied the divacancy-defect effect of armchair graphene nanoribbons with zigzag edges. It is shown that the existence of 585 divacancy defects do not change the metallic characteristics of graphene nanoribbon, while changing the energy band structures near the Fermi energy level. Moreover, the spatial orientations of the divacancy defects have obvious effect on the transport properties of armchair graphene nanoribbons: for armchair graphene nanoribbons with odd width, slanting divacancies defects weaken conducting performace of graphene nanoribbons, while graphene nanoribbons with vertical divacancies defects basically remain linear I-V characteristics and little decrease in conducting capacity；For armchair graphene nanoribbons with even width, inclined divacancy defects increase the conducting property of graphene nanoribbons, while graphene nanoribbons with vertical divacancy defects have I-V characteristics of the perfect graphene nanoribbons.