In this paper, a mesa-type 256×8 long-wavelength infrared detector is prepared by using InAs/GaSb type-II superlattice material with double barrieres structure. the area of each pixel is 25×25 μm2. The cut-off wavelength and dark current density of the detector at -0.05 V bias with liquid nitrogen temperature is 11.5 μm and 4.1×10-4 A/cm2, respectively. The power spectrum of low-frequency noise (1/f noise) at different temperatures have also been fitted by the Hooge model, and the correlations with dark current are extracted subsequently. The results shown that the 1/f noise of the detector is mainly caused by the generation-recombination current at a low reverse bias, however, when the reverse bias is high, the 1/f noise should be expressed by the sum of Igr noise and Ibtb noise which is ignored in the previous research. The 1/f noise-current correlation assessed in this work can provide insights into the low frequency noise characteristics of long-wavelength T2SL InAs/GaSb detectors, and allow for a better understanding of the main source of low-frequency noise.