The nano-TiO2 coating was applied to the surface of the fish pond to construct a recirculating aquaculture system consisiting of test group and control group. The effect of nano-TiO2 coating on purification of the wastewater in the water circulation treatment mode was studied. The influences of mass concentration of ammonia nitrogen in the raw water C0, DO and pH value on ammonia nitrogen degradation effiency were investigated. The results showed that after 48h treatment by test group of the recirculating aquaculture system with pH 7.0-7.8, TAN 14.2-15.3 mg/L, NO3--N 20.8-21.9mg/L and colonies number > 106/mL, ammonia nitrogen degradation reaction kinetics accordedwith the first-order kinetic equation. The reaction rate constant was 0.0697h-1, the half-life was 9.92h, and the ammonia nitrogen degradation and bacteriostatic effect were good. The order of the extent of influences of mass concentration of ammonia nitrogen in the raw water C0, DO and pH on ammonia nitrogen degradation in the test group was C0> DO>pH. When the mass concentration of ammonia nitrogen in the raw water C0 was 15 mg/L, DO was 6 mg/L and pH was 7.5, the ammonia nitrogen removal rate reached 41.9% when the test group of the recirculating aquaculture system was operated for 8h. The nano-TiO2 coating applied to the surface of the fish pond has a good purifying effect on the water body of the recirculating aquaculture system, and has a broad application prospect.