We report a joint theoretical and experimental study of several new thiophene-based poly(azomethine)s. Hybrid density functional theory (DFT) method was used to calculate the optimized geometry and electronic structure of poly(azomethine)s. Theoretical band gaps of the new thiophene-based poly(azomethine)s were in the range 2.33-2.67 eV, which are smaller than that of the phenylene-based polymer. The variation of the backbone ring (fluorene, carbazole, or naphthalene) or donor/acceptor side group on the phenylene ring significantly affected the dihedral angles and resulted in the variation of electronic properties (ionization potential, electron affinity, and band gap) of the poly(azomethine)s. Five soluble new conjugated poly(azomethine)s derived from the polymerization of 2,5-diformyl-3-hexylthiophene, (DFHT) with various diamines were prepared and characterized. The optical and electrochemical band gaps of the polymer films were in the ranges 2.21-2.28 and 2.13-2.24 eV, respectively. The trend of the effect of the backbone ring or side chain on the experimental electronic properties is in good agreement with the theoretical results. Our study demonstrates how the electronic properties of conjugated poly(azomethine)s can be tuned by the backbone ring or side group, which could be important for electronic or optoelectronic applications of the materials.