In this article, we demonstrate the strategy for receiving low-band gap conjugated polymers based on thiophene-fused boron dipyrromethene (TB) with homopolymer structure. A series of TB-based polymers and oligomers with low band gaps were synthesized by oxidation coupling. The obtained polymers and their oligomers exhibited strong absorption in the range from visible to near-infrared region around 400-2000 nm (epsilon = 168 000-26 000 M-1 cm(-1)) originated from efficient expansion of main-chain conjugations. From the results of cyclic voltammetry, it was revealed that the TB derivatives have low-lying HOMOs and LUMOs. Furthermore, the TB derivatives showed high stability in atmosphere.