The reduction reaction from Fe3+ to Fe2+ in solid catalysts during heterogeneous Fenton processes restricted the catalytic activity. In order to accelerate this reduction process, heterojunctions composed of Ni-doped Fe3O4 nanoparticles (OD) and two-dimension (2D) SnS2 nanosheets were successfully synthesized. The interactions between the S atoms in SnS2 and the cations (Fe3+, Fe2+ and Ni2+) in the solid Ni-doped Fe3O4 were demonstrated by experimental results. The heterojunctions formation accelerated the reduction from Fe3+ to Fe2+. The composite exhibited higher photo-Fenton activity than that of individual the Ni-doped Fe3O4 and SnS2, and the mixture of Ni-doped Fe3O4 and SnS2. The RhB degradation degrees are about 97% and 47% for the composite and the mixture within 60 min, 28% and 89% for the Ni-doped Fe3O4 and the SnS2 within 180 min, respectively. The composite displayed excellent stability for the degradation of RhB. The degree of RhB degradation was higher than 90% in the pH range from 3.42 to 9.06 for 60 min. Simultaneously, the composite showed excellent photo-Fenton catalytic activity for different dyes as cationic molecule MB and anionic dye MO. A possible photocatalytic mechanism was proposed.