A series of AgIO3 modified BiOI/CoFe2O4 heterojunction photocatalysts synthesized by a solvothermal and subsequent deposition-precipitation method were utilized to remove gaseous Hg-0 from simulated flue gas under fluorescent light irradiation. The effects of AgIO3 content, photocatalyst dosage, solution temperature, fluorescent lamp irradiation, pH value, inorganic anions, and SO2 and NO on Hg-0 removal performances were investigated in detail. Moreover, the ternary AgIO3-BiOI/CoFe2O4 composites were characterized by XRD, magnetic hysteresis, N-2 adsorption-desorption, SEM, TEM, XPS, DRS, ESR, and photocurrent analyses. The results indicated that the AgIO3-BiOI/CoFe2O4 materials possessed enhanced visible-light-driven photocatalytic activities for Hg-0 removal, which were much higher than those for AgIO3 and BiOI, and the Hg-0 removal efficiency by optimum AgIO3(7%)/BC can reach as high as 99%. The AgIO3 content, solution temperature, FSL irradiation, and SO2 all exhibited significant effects on Hg-0 removal. AgIO3(7%)/BC showed good stability and remained highly efficient after four runs. The characterization suggested that AgIO3 was tightly anchored onto the BiOI/CoFe2O4 surface to form a AgIO3-BiOI/CoFe2O4 heterojunction photocatalyst, and the presence of a small amount of AgI might play a vital role for enhanced activity of AgIO3-BiOI/CoFe2O4 photocatalysts. The scavenging experiments of reactive species demonstrated that the superoxide radicals (O-center dot(2)-) and holes (h(+)) were the main oxidant for efficient removal of Hg-0.