Iridium benzothiophen complexes with red light emission has strong electroluminescence performance, which have been widely applied in photoelectric display field. Take 2-(benzothiophen-2-yl)- quinoline as basic ligand, the electronic structures and spectroscopic properties of a series of isomer iridium (btq)2Ir(pic) [btq=2-(benzothiophen-2-yl)quinolin(1), 3-(benzothiophen-2-yl)isoquinoline(2), 1-(benzothio- phen-2-yl)isoquin/oline(3), pic=picolinate ancillary ligands] complexes have been investigated theoretically. Their structures of S0 and T1 were optimized by the B3LYP and CIS methods, the TD-DFT method with the CPCM model were used to obtain their absorption and phosphorescent emission spectra in CH2Cl2 media. The results revealed that the optimized structural parameters agreed well with the corresponding experimental results. The lowest-lying absorptions and emissions are at 488 (1), 455 (2), 485 (3) and 679 (1), 642 (2), 683 nm(3), respectively. The highest occupied molecular orbitals were localized mainly on the d orbital of the metal and the π orbital of the btq ligand for 1-3, while the lowest unoccupied molecular orbitals were mainly composed of π* orbital of the btq ligand. Therefore, the lowest-lying absorptions and emissions were assigned to the metal to btq ligand charge transfer (MLCT)/intra-ligand charge transfer (ILCT) transition. The change of benzene ring position has no significant effect on the main structure of these complexes, but both steric hindrance and conjugation have significantly effect on its luminous color.