InAs/GaSb type-II superlattice (T2SL) infrared detectors have great advantages in the field of long-wave infrared detection due to their broad-band detection capability, high material uniformity, suppressed Auger recombination rates and flexible energy band design. However, the performances do not reach the theoretical prediction due to the large dark current. The pπBn structure is designed to add a monopole barrier between the absorption layer and the contact layer of the detector to suppress the G-R dark current and tunneling dark current. In this paper, the superlattice band structure of absorption layer, barrier layer and contact layer are studied theoretically separately. This study simulates a InAs/GaSb T2SL with pπBn structure and study its doping concentration of the absorption layer, the doping concentration of the barrier layer and the thickness of the barrier layer to reduce the dark current. Through optimizing the doping concentration of the absorption layer, the thickness and the doping concentration of the barrier layer, the pπBn structure InAs/GaSb T2SL with dark current density of 8.35×10^-7 A/cm² is obtained, which reduces the dark current by one order of magnitude as compared with that of the structure before optimization. The research process not only provides guidance for designing the low dark current with pπBn structure device, but also develops a systematic method to optimize the dark current of superlattice device.