A novel semiconducting polybenzanthrone, with relatively high electrical conductivity and excellent thermal stability, was successfully electrosynthesized by direct anodic oxidation of its monomer benzanthrone in acetonitrile solution containing Bu4NBF4 or boron trifluoride diethyl etherate (BFEE) acting as the supporting electrolyte. As-formed polybenzanthrone films showed good redox activity and nice structural stability even in concentrated sulfuric acid. UV-vis, FT-IR, and H-1 NMR spectral analyses and MALDI-TOF MS results, together with quantum chemistry calculations, proved that the polymer chains grew mainly via the coupling of the monomer at C(3) and C(11) positions. The fluorescence properties of both doped and dedoped polybenzanthrone were greatly improved in comparison with that of the monomer. Furthermore, both doped and dedoped polybenzanthrone, dissolved in common organic solvents, with fluorescence quantum yields as high as 0.52, also emitted strong and bright green or yellow-green photoluminescence at excitation of 365 nm UV light. All these results indicate that the striking polybenzanthrone films as obtained have many potential applications in various fields.