Nitrogen-rich graphite carbon nitride (g-C3N5) has shown its great potential in the field of photocatalysis due to its narrow bandgap (~2.2 eV) and its ability to absorb visible light with a wavelength of ≤660 nm. However, a single g-C3N5 semiconductor has bottlenecks such as high photogenerated carrier recombination rate and low quantum efficiency. The construction of heterojunction to regulate the interfacial charge migration path has become an effective strategy to improve its photocatalytic performance. In this article, the structures, charge transport mechanisms and modification strategies of g-C3N5 based heterojunctions are summarized, and the photocatalytic degradation performance and mechanism on organic pollutants in aqueous solution are established. In addition, based on the current development status, it is proposed that in the future, environmentally friendly inorganic semiconductors should be developed for the construction of heterojunctions, a mode of "machine learning screening- DFT in-depth analysis-experimental verification" should be established to accelerate the development and optimization of high-performance heterojunctions, efficient and accurate charge detection methods should be applied to reveal the structure and charge transfer mechanism of heterojunctions, and the long-term continuous experiments should be conducted to evaluate the stability and applicability of photocatalysts.