Interaction between graphene divacancies and C2H2, which commonly is used to recover the vacancies, was investigated by density functional theory simulations. Physisorption with no charge transfer between C2H2 and graphene surface was found. Molecular dynamics simulations show that the potential energy of the system decreases when C2H2 moves from the edge to the center of divacancy, and C2H2 ultimately fills the divacancy with no energy barrier. The torque acting on C2H2 rotates it to fit the orientation of the divacancy. This result offers an explanation for experimental results showing the ability of C2H2 to repair defects in graphene. (C) 2013 Elsevier B. V. All rights reserved.