The electronic structures and spectroscopic properties of the four tridentate cyclometalated Au(III) complexes [Au((C) over cap(N) over capC CPh] (1), [Au((N) over cap(N) over capC CPh](+) (2), [Au((N) over tilde(N) over tildeC)C CPh](+) (3), and [Au((N) over cap(C) over cap )C CPh](+) (4) [H (C) over cap(N) over cap CH=2,6 -diphenylpyridine, NCHCH = 3-(2-pyridyl)biphenyl, NNCH = 6-phenyl-2,2'-bipyridine, (N) over capC (H) over cap CH=1,3-di(2-pyridyl)benzene] were calculated to explore their spectroscopic nature. The geometry structures of 1-4 in the ground and excited states were optimized under the density functional theory (DFT) and the single-excitation configuration interaction (CIS) level, respectively. The absorption and emission spectra in CH202 solution were calculated by the time-dependent density functional theory (TD-DFT) with the PCM solvent model. As revealed from the calculations, with the variation of pyridyl in position and the number, the electron-accepting ability of pyridyl in 1-4 are different. With increasing the electron-accepting ability of pyridyl, the HOMO-LUMO energy gaps of 1-4 decrease, and the lowest-energy absorption bands and emission bands are red-shifted in the order 1 < 2 < 4 < 3. All of the lowest-energy absorptions are assigned as the LLCT character, and the solvent polarity has little impact on the absorption spectra. The 477 nm emission of 1 arises from the (ILCT)-I-3 transition, whereas the 517 and 634 nin emission of 2 and 3, respectively, corne from the (LLCT)-L-3 and (ILCT)-I-3. In addition, the 577 nin emission of 4 is assigned as (LLCT)-L-3/(LMCT)-L-3 character.