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The electronic structure and optical properties of Ca3(Mn1−xTix)2O7 (x=0, 1/8, 2/8, 3/8, 4/8) were studied by first-principle calculations within the generalized gradient approximation approaches (GGA). The lattice constants of Ca3(Mn1−xTix)2O7 increase with the increase of Ti4+ content caused by the substitution of Ti4+ with larger ionic radius for Mn4+. Ca3(Mn1−xTix)2O7 is a direct band gap semiconductor, and the band gap (Eg) increases with the increase of Ti4+ content. From the density of states, the introduction of Ti-3d states can weaken the effects of Mn-3d states on the bottom of conduction band and has little influence on O-2p states on the top of valence band. The introduction of nonmagnetic Ti4+ ions can weaken the magnetism of Ca3(Mn1−xTix)2O7. According to the Mulliken population analysis, it is found that the introduction of Ti4+ enhances the electronic accepting capacity of oxygen ions and enhances the electronic losing capacity of manganese ions. The bond strength of Ti–O covalent bond is stronger than that of Mn–O covalent bond. Furthermore, the optical properties of Ca3(Mn1−xTix)2O7 was calculated. As Ti4+ content increases, the absorption edge of Ca3(Mn1−xTix)2O7 has a blue shift, the static refractive index n0 decreases, the static dielectric constant ε1(0) decreases, the position of loss peak moves to higher energy.