Sulfur and selenium co-doped graphitic carbon nitride (SSCN) with efficient photocatalytic activity was synthesized by synchronously introducing sulfur and selenium atoms into the melon structure of g-C₃N₄ (GCN) via a facile solid-phase thermal reaction of GCN and SeS₂. The as-prepared SSCN possesses a larger specific surface area with a richer pore structure that provides more active centers for catalytic reaction. More importantly, the asymmetric structure of SSCN due to introducing sulfur and selenium not only maintains an easier activation of π-π* electron transition but also awakens the n-π* electron transition in g-C₃N₄. Moreover, the n-π* electron transition of SSCN can be controlled through changing the amount of SeS₂, which can greatly extend the photo-response range to 600 nm. As a result, the SSCN samples show an excellent photo-degradation performance for typical antibiotic of tetracycline hydrochloride (TC). The specific degradation route and main intermediates of TC based on liquid chromatograph mass spectrometer (LC-MS) analysis are also investigated and discussed.