In this study, a carbonized aerogel (CA) decorated with Mn-FeOOH hybrid nanoparticles was prepared and has been used as a better heterogeneous photo-Fenton catalyst. Mn doping accelerated the regeneration of Fe²⁺ and promoted the decomposition of H₂O₂ while producing many hydroxyl radicals (·OH), which solved the mass transfer problem in the traditional heterogeneous Fenton system. The amount of·OH in the Mn-FeOOH@CA/H₂O₂ system within 40 min was 2.4 times higher than that in the FeOOH@CA/H₂O₂ system, which further indicates that·OH was the main active species. High-porosity CA has been designed as an electron transport channel. During photocatalysis, electron transfer occurred between the Mn-FeOOH composite material and CA. The Fe²⁺ could be used as reaction sites to promote the activation of H₂O₂ on the surface of 1-Mn/FeOOH, and achieved 100 % As(III) degradation efficiency within 25 min. The catalyst maintained more than 80 % of its original oxidation capacity after five cycles of experiments, which indicates that it has good durability. This work is expected to provide rational design of heterometallic doped materials with oxygen vacancies to treat arsenic pollution.