A highly reactive hollow tubular g-C3N4 isotype heterojunction (SCN-CN) was designed to enhance visible light absorption and manipulate the directed transfer of electrons and holes. The results of UV–vis DRS, XPS valence band and DFT theoretical calculations indicated S doping increases the visible-light absorption capacity and changed the ba nd gap structure of g-C3N4 (CN), resulting in the transfer of electrons from the CN to the SCN and holes from the SCN to the CN under visible light. In addition, the tubular structure of the SCN-CN facilitated the transfer of electrons in the longitudinal direction, which reduced charge carrier recombination. Furthermore, the optical properties, electronic structure, and electron transfer of SCN-CN were also studied by experiments and theoretical calculations. The antibiotic tetracycline hydrochloride (TCH) and dye Rhodamine B (RHB) were subjected to evaluate the photocatalytic performance of SCN-CN. The scavenger tests and ESR data showed that the h+, ·O2− and ·OH worked together in the photocatalytic process. Moreover, the photocatalytic degradation pathway was analyzed by LC-MS. This study synthesized a hollow tubular CN isotype heterojunction with high visible-light photocatalytic performance and provided a theoretical basis for CN isotype heterojunction.