A principle of the enhancement of CO adsorption was developed theoretically by using density functional theory through doping Al into graphene. The results show that the Al doped graphene has strong chemisorption of CO molecule by forming Al-CO bond, where CO onto intrinsic graphene remains weak physisorption. Furthermore, the enhancement of CO sensitivity in the Al doped graphene is determined by a large electrical conductivity change after adsorption, where CO absorption leads to increase of electrical conductivity via introducing large amount of shallow acceptor states. Therefore, this newly developed Al doped graphene would be an excellent candidate for sensing CO gas. (C) 2008 Elsevier B.V. All rights reserved.