Abstract: Fe₂O₃-SnO₂ photocatalysts were synthesized by co-precipitation method. The morphology and crystal pattern of some prepared catalysts were characterized by XRD and SEM techniques which demonstrated that the prepared catalysts were quartet rutile structure. The effects of different factors on the degradation efficiency of ammonia nitrogen in mariculture wastewater were investigated, including Fe₂O₃-SnO₂ catalyst dosage, the molar ratio of Fe₂O₃ and SnO₂ , calcination temperature, calcination time, the initial concentration of ammonia-N, pH value, the concentration of H₂O₂ and catalytic reaction time. An orthogonal experiment was carried out under UV-light. The optimal combinations were confirm with results that the dosage of catalyst was 0.4 g/dm³, calcination time was 3.0h, the molar ratio of Fe₂O₃ and SnO₂ was 1∶2, initial concentration of ammonia-N was 50mg/dm³ and photocatalytic degradation reaction time was 2.0h. The influence orders of degradation are listed as follows, the molar ratio of Fe₂O₃ and SnO₂ > calcination time> photocatalyst dosage> initial concentration of ammonia-N> reaction time. The removal rate of ammonia-N is capable to reach 85.1%, the removal rate of ammonia-N in seawater is expected to reach 82.3% under the same conditions.