In order to study the adsorption of NO ₂on pristine graphene and doped graphene (N-doped, Zn-doped, and N-Zn co-doped), we have simulated the adsorption process by applying the first-principles plane-wave ultrasoft pseudopotentials of the density-functional theory. The adsorption energy, Mulliken distribution, differential charge density, density of states and optical properties of NO ₂molecules adsorbed on the graphene surface were calculated. The results show that the doped graphene surface exhibits higher sensitivity to the adsorption of NO ₂compared with the pristine graphene surface, and the order of adsorption energies is as follows: N-Zn co-doped surface > Zn-doped surface > N-doped surface > pristine surface. Pristine graphene and N-doped graphene surfaces have weak interactions with NO ₂and are physical adsorption. Zn-doped and N-Zn co-doped graphene surfaces form chemical bonds with NO ₂and are chemisorbed. In the visible range, among the three doping modes, the N-Zn co-doped surface is the most effective for improving the optical properties of graphene, with the peak absorption and reflection coefficients improved by about 1.12 and 3.42 times, respectively, compared with those of pristine graphene. The N-Zn co-doped graphene not only enhances the interaction between the surface and NO ₂, but also improves the optical properties of the material, which provides theoretical support and experimental guidance for NO ₂gas detection and sensing based on graphene substrate.