Abstract: Selecting the sediments of Yangzonghai Lakeside Wetland in Yunnan as the research object. The concentration of exogenous arsenic was selected from 0.00, 0.01, 0.05, 0.10, 0.25, 0.50, and 1.00 mg/L. The experimental time was set to short-term (1−72 h) and long-term (7−15 d). Exploring the influence of exogenous arsenic input on phosphorus release and morphological transformation of sediments. The results show that when the concentration of exogenous arsenic is 0−0.25 mg/L, the sediment adsorption rate of arsenic is faster, mainly based on physical adsorption. At 0.25−1 mg/L, the adsorption rate of arsenic by sediments is slowed down, mainly by chemical adsorption. With the increase of exogenous arsenic concentration, the release amount of phosphorus in the sediment increase first and then decrease. When the concentration of arsenic is 0.25 mg/L, the maximum amount of phosphorus released from sediment is 0.092 mg/L, exceeding the standard value of Class III water standard for surface water quality and environmental standards. The increase of exogenous arsenic concentration causes the phosphorus form in the sediment to change from inert to active. The increase of Al-P and Fe-P content is significantly correlated with the concentration of arsenic. The entry of exogenous arsenic leads to an increase in the release of phosphorus from the sediment and the conversion of the phosphorus form from inactive to active, increasing the ecological risk of arsenic and phosphorus.