Effects of an electric field on CO oxidation of Au-embedded graphene are investigated using first-principles method. Results of our calculations show that the initial step of the reaction is more likely to proceed via the Langmuir-Hinshelwood mechanism in the presence of the field, and the reaction barrier can be tuned continuously by the electric field. However, the applied electric field makes it more difficult for the product of the reaction, CO2, to desorb from the reaction site. These two competing effects make an electric field not entirely advantageous in controlling the activity of Au-embedded graphene for CO oxidation reaction. Nevertheless, the findings of our study provide a basis for further investigation on control of chemical reactions by electric fields. Effects of an electric field on CO oxidation of Au-embedded graphene are investigated using first-principles method. Results of our calculations show that the initial step of the reaction is more likely to proceed via the Langmuir-Hinshelwood mechanism in the presence of the field However, the applied electric field makes it more difficult for the product of the reaction, CO2, to desorb from the reaction site. These two competing effects make an electric field not entirely Actions in controlling the activity of Au-embedded graphene for CO oxidation reaction. Nevertheless, the findings of our study provide a basis for further investigation on control of chemical reactions by electric fields.