The electronic and optical properties of Au, Cu, Sb doped CdTe systems were studied based on density functional theory. Au, Cu and Sb doped CdTe systems all exist stably. The hybridization of transition metal atoms with Cd atomic orbitals reduces the band gap of CdTe and improves the utilization of visible light by CdTe. The lower energy required to jump from the valence band to the conduction band promotes the migration of more photogenerated electrons, which greatly improves the optical properties of doped CdTe. Among the three systems, Sb/CdTe system shows the most significant increase of absorption coefficient in the visible light range, with photogenerated electron and hole mobilities increasing by a factor of 5.97 times and 15.54 times compared with CdTe system, respectively. The mechanism of the enhancement of the optical properties of Au, Cu, and Sb doped CdTe is theoretically revealed by calculating the band, density of states, electron population, optical absorption function, and carrier mobility.