The invention provides a preparation method for arborization silver. The preparation method comprises the following steps that a first solution is provided, and the first solution comprises agarose dispersed into a first solvent; a second solution is provided, and the second solution comprises silver salt dispersed into a second solvent; the first solution and the second solution are mixed, and the mixed solution is cooled and subjected to standing to obtain agarose/nano-silver plural gel; and the agarose/nano-silver plural gel is made contact with metal foil, so that the arborization silver is prepared. According to the preparation method for the arborization silver, raw materials for preparing the arborization silver are easy to obtain, the operation is simple and convenient, reaction conditions are mild, effects of safety and environment protection are achieved, the size of the product is large and the morphology of the product is stable, and no other reducing agent or annexing agent need to be introduced.