A preparation method for an adsorbing agent is characterized in that at the presence of polyhydric alcohols or sugar compounds, hydrophilic carriers are loaded with metal ions of at least one of iron compounds, copper compounds and zinc compounds through ion exchange or dipping, and the adsorbing agent is obtained through high-temperature roasting. The invention further provides a method for adsorption separation of chlorine in grease. Adsorption separation of the chlorine in the grease is achieved through the adsorbing agent in a static adsorption or dynamic adsorption or fluidized bed mode. The adsorbing agent is prepared through the preparation method. The grease is at least one of animal and vegetable oil, waste cooking oil, acid oil, fatty acid methyl ester and fatty acid ethyl ester fuel. The content of the chlorine in the grease is smaller than 50 ppm.