In order to study the photo-Fenton properties of FeOCl combined with carbon materials, g-C
3N
4/FeOCl nanocomposites are prepared by a simple calcination method according to the different composite mass ratios of g-C
3N
4 and FeCl
3·6H
2O. Composition, structure, and optical properties of the composite samples tested by XRD, SEM, TEM, XPS, UV-vis, EIS, and Transient photocurrent testing. The results show that the g-C
3N
4/FeOCl composite has a layered nanorod stacking structure with the good light response and carrier separation capability. When the composite ratio of g-C
3N
4 to FeOCl is 1∶20, it exhibits excellent photo-Fenton performance, and the degradation rate of rhodamine B (RhB) reaches 92.4%. And after three cycles, the efficiency of the composite material in degrading RhB remained at 80.1% that showing good stability. Based on the experimental results, the Z-type heterojunction between g-C
3N
4 and FeOCl was proposed to improve the separation efficiency of photogenerated carriers, and the possible mechanism of photo Fenton degradation of RhB by Z-type heterojunction was discussed.