Density functional theory (DFT) calculations are carried out to investigate the effect of point defects on acetylene hydrogenation reaction over Ni(111) surface with three different defect concentrations (DC = 0.0500, 0.0625, and 0.0833), compared with the perfect Ni(111) surface. The adsorptions of C2 species and H atoms and the mechanism of acetylene hydrogenation via the ethylene pathway are systematically analyzed. The results indicate that the existence of defects will make C2 species and H atoms more inclined to adsorb near the defects. Introducing an appropriate amount of point defect concentration can enhance the catalytic activity and ethylene selectivity of Ni. In this work, DC = 0.0625 Ni(111) surface has the highest catalytic activity and selectivity of ethylene. This work provides useful theoretical information on the effect of defects on acetylene hydrogenation and is helpful for the design of Ni and related metal catalysts with defects.