Bismuth oxide iodate (BiOIO3) has recently been discovered to apply to the research on photocatalytic territory in environmental pollutants solution. However, its weak response to the visible light and high recombination rate of electron-hole pairs have been the stumbling block on the road to application. In this work, to remit the drawbacks, carbon modified BiOI/BiOIO3 heterostructures are prepared by a facile hydrothermal method and a simple calcination method. The prepared structure can effectively promote the separation of charge and suppress recombination of electron-hole pairs. When the ternary photocatalyst is applied to remove gas phase elemental mercury (Hg-0) in the condition with visible light irradiating, it exhibits excellent photocatalytic properties. Compared with pure BiOIO3, the removal efficiency of ameliorated samples has been drastically increased. On the basis of the results of experiments, the possible charge migration and recombination mechanism are put forward. As a novel and promising method to enhance photocatalytic performance, this method presents a strategy, which yields tremendous benefits in designing efficient photocatalyst and environmental remediation applications. [GRAPHICS] .