Two series of osmium(II) complexes with different substituent groups (-CF3, -N(CH3)(2)) have been studied by using the density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, to investigate their electronic structures, absorption, and emission properties. The influence of different substituted groups on their photophysical properties has also been explored. The lowest energy absorption and emission wavelengths calculated are in good agreement with the available experimental values. Besides, ionization potential (IP), electron affinities (EA), and reorganization energy () were calculated to evaluate the charge transfer and balance properties between hole and electron. It is expected that the theoretical studies could provide valuable information for the phosphorescent osmium(II) material for use in the organic light-emitting diodes.