Delafossite-structured CuAlO2 materials with and without vacancy defects were investigated comparatively using the first principle calculation method. The method based on the density functional theory, has been carried out to search the systems’ ground states and supplies the corresponding electronic properties. In the process of calculations, ultrasoft pseudo-potentials and PBE-GGA functionals are chosen for the atoms and exchange-correlation interactons between electrons, respectively. The geometry optimization shows the Al vacancy causes a larger lattice deformation than the vacancies of Cu and O atoms. The results of Mulliken charge also verify this conclusion. The calculations of vacancy formation energy and elastic constants indicate the Cu vacancy has the lowest formation energy, the highest Pugh ratio and the smallest Zener anisotropy factor, which means the introduction of Cu vacancy can improve the functional applications of Cu-based delafossites, e.g. p-type conductivity, ductility, etc.