The adsorptions of CO molecules on the pristine, defective, In-doped and Sb-doped graphene were investigated through the density functional theory (DFT) calculations. The stable geometries, electronic properties and charge transfers of the graphene based systems were calculated to study the interaction between the adsorbed CO molecule and the built material. It was found that only the weak physical adsorption took place when the CO was placed on the pristine graphene and the doped graphene. On the contrary, the defective graphene exhibited a high affinity to the CO molecule, acting as a potential sensing material to interact with CO through a strong chemisorption with the high adsorption energy of similar to 1.996 eV, which was little affected by the increased coverage effect of CO molecules. Moreover, this adsorption energy was calculated to be enhanced by similar to 62.6% and there was extra charge of 0.31 e transferred from the adsorbed CO molecule to the defective graphene under the negative electric field. Our research revealed that the applied electric field could be an effective method to improve the gas sensing performance of defective graphene.