A reagent is provided for removing mercury (Hg). The reagent contains metal carbonates compound with layers structure. The contents of metals of reagent can be adjusted using this method. The reagent can be manufactured with kilogram grade per batch. The common ions, like Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn, etc., can be contained in the reagent. The manufacture method provides a low-cost way for the Hg sorbent and the content ratio of metal oxides can be higher than 50 wt %. The manufacture is operated at a temperature more than 200° C. and can be integrated with existing technology such as denitration catalysts in industry for removing Hg. In another word, the present invention fabricates a mercury-removing reagent of metal-M/aluminum carbonates (M-Al—CO3), which can be potentially combined with commercially selective catalytic reduction (SCR) catalysts for developing medium-high-temperature mercury-removing reagent with mercury-removing efficiency further enhanced.