Effect of changes in the overlying water pH and total phosphorus concentrations on arsenic migration was unclear for sediments which contained high arsenic and iron salts. To figure out the rules of arsenic mobilization under different pH, initial pH and initial phosphorus concentrations, the experiments were conducted with the sediments which contained high arsenic and iron salts. Results showed that: When sediments exposed to overlying water of pH=10 and pH=11, leaching speed of arsenic enhanced suddenly after 11 days and 6 days, respectively. When sediments exposed to alkaline environment, stronger the alkalinity was, much quicker the leaching was,with more arsenic migration from the sediments. From the indoor experiments, lake alkalinization may increase the risk of arsenic mobilization from the sediments. However, there was little effect of pH which ranging from 4 to 8 on arsenic mobilization. When the concentration of phosphorus in overlying water was less than 0.5mg/L, the competitive adsorption of phosphorus had little effect on arsenic mobilization.