Abstract: Four arsenic pollution treatments (0, 50, 150, 600 mg/kg) and 4 exogenous phosphorus treatments (0, 0.2, 2, 20 mg/L) were set up to simulate arsenic pollution wetland environment.The physical and chemical properties of the sediment, T-As, arsenic form, phosphatase, urease and dehydrogenase were analyzed after 60 days cultivation. The effects of exogenous phosphorus inputs on the distribution of inorganic arsenic in sediments and soil enzyme activity in arsenic-contaminated sediments were analyzed. The results showed that soil pH, EC, DO and Eh were significantly affected by exogenous phosphorus. With the increase of exogenous phosphorus, the total arsenic was decreased and the bioavailability coefficient decreased with the increase of the exogenous phosphorus. The toxicity degree of arsenic to 3 soil enzyme was: phosphatase > dehydrogenase > urease, exogenous phosphorus can enhance dehydrogenase activity and phosphatase activity, urease is not sensitive to arsenic. The urease activity was inhibited with 600 mg/kg arsenic treatment, and urease activity was activated by exogenous phosphorus. The phosphatase activity has a significant negative correlation with the concentration of arsenic in sediment, and exogenous phosphorus could increase the phosphatase activity in sediment. Exogenous phosphorus could reduce the total arsenic content in sediment and the bioavailability of arsenic were increased by the phosphorus, soil enzyme activity were protected by phosphorus.