Abstract: The tensile mechanical properties of zigzag and armchair single graphene sheets were investigated by molecular dynamics simulation using the Tersoff bond-order interatomic potential. The tensile stressstrain curves of the sheets were obtained and analyzed. The deformation mechanism of the sheets under tension was also studied. Results show that the sheets are not perfectly flat after relaxation, but exhibit microscopic corrugations such as waves and ripples. The Young’ s modulus of the zigzag and armchair sheets are 1031.36GPa and 1058.42GPa, respectively, which are in very good agreement with results reported in the literature. It is also found that the defects are formed at the edges of graphene sheets under tension. These are induced by the transformation of the hexagonal carbon rings into pentagons. With a further increase in strain and number of defects, the graphene sheets finally fail through bond breaking.