The invention discloses a green preparation method of a petal-shaped silver nanosheet, and belongs to the technical field of preparation of precious metal nano materials. The preparation method of thepetal-shaped silver nanosheet is taken into consideration from green chemistry, and no toxic chemical reagent is used in the preparation process. The method comprises the following steps of taking water as a solvent, constructing a mixed solution reaction system by using micromolecular organic acid and polyethylene glycol under normal-temperature and normal-pressure conditions, the water-solublesilver salt is a silver source, the petal-shaped silver nanosheet with controllable morphology size and good uniformity is prepared by using a small molecule polyphenol compound and a mixture thereofin the tea leaf extracting solution as a reducing agent, the diameter of the petal-shaped silver nanosheet is 400-600 nm, the thickness of the petal-shaped silver nanosheet is less than 80 nm, and thenanosheet has good antibacterial property. The preparation method is simple and easy to operate, and has the advantages of low cost, low toxicity, low energy consumption and high yield.