Structure and electronic properties of rocksalt CdO are studied by using density functional theory (DFT), in which the exchange correlation functions are described with generalized gradient approximation (GGA), local density approximation (LDA), B3LYP, HSE06 and HSE03. The ground state properties of the rocksalt CdO have been subjected to investigate by the calculated band structure and density of state. The results reveal that CdO is an indirect wide band gap semiconductor, and a very similar dispersion of calculated energy levels is also found around Fermi level. In addition, it is obvious that the hybrid-exchange functions are more accurate than the GGA and LDA functional for the band gap of the rocksalt CdO. Particularly to the Burstein–Moss effect and the calculated effective mass conform to existing experimental results, which have offered theoretical reference for design and large scale application of the rocksalt CdO materials