The invention discloses a synthesis method for an elemental mercury sorbent, comprising the steps that: a solvent and a modifying agent are added into a reactor, 20-50 meshes of attapulgite powder isadded subsequent to the dissolution of agents, 0.04-0.1 kg. of attapulgite are added into the solvent per liter, the mass ratio of the added modifying agent to the attapulgite is 1:3-1:50, and filtration and drying are implemented after uniform mixing, wherein, the solvent is deionized water, acetone, methanol or ethanol; the modifying agent is any one of the group consisting of copper chloride, sodium chlorate, potassium bromide, potassium iodide, calcium thioglycolate, cysteine, glutathione, dimercaptopyridine and 3-mercaptopropyltrimethoxysilane. The sorbent synthesized according to the method is natural mine, which is low in price, easy in acquirement and free from generating secondary pollution to environment and causing no influence on economical efficiency of fly ash in power plant;the used modifying agent is nontoxic and harmless, the synthesis for the sorbent is simple and easily operated, and the sorbent is obvious in removing elemental mercury and can reduce the concentration of the elemental mercury in smoke from coal-fired power plant by over 90% to be thereby harmless to environment during the production.