In this work, sea urchin-like magnetic Fe3O4@CA/BNNS/AgNP composite microspheres were successfully prepared. The photocatalytic performance of composite microspheres for the organic dye rhodamine B (RhB) was systematically investigated under different conditions, and the catalytic degradation rate of RhB was as high as 95% within 60 min; after three cycles of recycling, the degradation rate of RhB was reduced by only 8%. The main active agents in the reaction are e– and •O2–. Fe3O4@CA/BNNS/AgNP microspheres prepared in this study exhibit photocatalytic and electrochemical properties, making them easy to separate. This work is not limited to the development of Fe3O4-based catalysts but also is expected to provide ideas for the research and progress of photocatalytic composite catalysts with electrochemical properties.