We studied the optical luminescence properties of Li2TiO3: Mn4+ based on first-principles calculations. The optical luminescence properties such as Mn-O distance, molecular orbital (MO) energy, crystal field splitting, multiplet energy levels, and Coulomb interaction are discussed in detail. The impact of lattice relaxation was examined through geometry optimizations based on first-principles band-structure calculations using Cambridge Serial Total Energy Package (CASTEP) software. Both Discrete Variational-X alpha (DV-X alpha) and the Discrete Variational Multi-electron (DVME) software were used to estimate the optical luminescence properties. Here we also predicted the optical luminescence properties of Li2TiO3: Cr3+ The results imply that the multiplet energy levels tend to decline in the order of Mn4+ to Cr3+ The integral Coulomb's decreasing tendency is in excellent agreement with the declining tendency of E-2, T-2(1), T-2(2) energies of Li2TiO3: Mn4+ and Li2TiO3: Cr3+.