In this article, P-g-C3N4/TiO2 (the protonated g-C3N4 is noted as P-g-C3N4) heterojunction photocatalytic materials with hollow sphere structure were synthesized mainly by high-temperature calcination and secondary hydrothermal methods. To obtain highly efficient heterojunction catalytic materials with more uniform surface compounding, we protonated and exfoliated ultrasonically the obtained g-C3N4 before compounding further, which changed its morphology while retaining its semiconductor properties and optical band gap unchanged, and finally obtained the ultra-thin nanoflake structures. On this basis, an optimal proportion of the highest catalytic activity between these two substances was explored by degrading RHB. It was found that the highest catalytic activity of the complexes was achieved at 110 min with a weight ratio of 0.1 of P-g-C3N4 to TiO2 after protonating under the same conditions, and complete degradation was reached at 110 min. Afterward, to further investigate its physicochemical properties, we made various characterizations and proposed a suitable catalytic mechanism of Z-scheme regarding its excellent catalytic properties.