In this work, a novel magnetic photocatalyst Dy(OH)3/ZnO/SrFe12O19 (DZS) was prepared by simple hydrothermal method. Especially, 15-DZS-5 (Dy(OH)3 15%, SrFe12O19 5%) had the highest photocatalytic activity, and could completely degrade RhB when exposed to simulative sunlight for 70 min. Furthermore, 15-DZS-5 has the widest photoresponse range, the narrowest band gap, the lowest electron hole recombination rate and the best conductivity due to the photosensitization effect of SrFe12O19 and Dy(OH)3 successfully separating the electrons and holes of ZnO by photoelectron capture. In addition, the saturation magnetization of 15-DZS-5 is 3.9 emu/g, and the degradation of RhB is over 88% after five cycles, showing good magnetic recovery and stable photocatalytic activity. ·OH and ·O2- were the chief active groups in the photocatalytic RhB with 15-DZS-5 sample, and the influence of ·OH was more significant.