Gold nanoparticles (GNPs) are the subject of intensive studies and applications in biology and medicine. Functionalization facilitates targeted delivery of these nanoparticles to various cell types, bioimaging, drug delivery and also detection of biomolecules such as DNA. Therefore, investigated the adsorption of DNA bases as DNA building blocks on the Au are important. In this work, the adsorption activities of different distinct surface-models of a typical spherical gold nanoparticle (Au(111), Au(100) and Au(110)) for the adsorption of the DNA bases (adenine (ADE) and cytosine (CYT)) were investigated in both gas phase and water, separately. It was found that the adsorption energy ( E ad ) and adsorption geometry of the bases depend strongly on the kind of surface-model so that the Au (110) surface show higher adsorption affinity for both the ADE and CYT in the gas phase and water. Comparison of the E ads of bases, calculated in the gas phase, with those in water showed that the electrostatic field of solvent decreases the E ads of bases especially for the Au (110) surface model. The adsorption geometry of the CYT showed strong dependency on the kind of surface model compared to ADE. Also, the calculations showed that the direction and amount of charge transfer between the base and nanoparticle strongly depends on the kind of surface model, environment and base. There is a net charge transfer from the Au (111) surface of nanoparticle to the ADE while the net charge transfer takes place from the ADE to the Au (110) and Au (100) surfaces models of nanoparticle in the gas phase. In the case of CYT, the net charge transfer is from the CYT to three surface models in the gas phase. In water environment, the direction of charge transfer between the ADE and CYT, and Au (100) was reversed. The quantum theory of atoms in molecules (QTAIM) analysis was employed to determine the bond paths between the bases and model surfaces to see how the number of bond paths and the electron density at the bond critical points (BCPs) change with the kind of surface. The infrared (IR) spectra of the bases on the model surfaces were calculated and compared with each other and the IR spectra of the isolated bases. It was found that the symmetric and unsymmetric stretching of the N-H of NH 2 group, C-H stretching of the rings and C=O stretching of bases can be used for the discrimination of the selected surface models.