Abstract: A water-soluble shopping bag and a preparation method thereof. The water-soluble shopping bag consists of the following components according to the following parts by weight: 100 parts of polyvinyl alcohol, 8-20 parts of a composite plasticizer; 10-30 parts of a polysaccharide and the derivative thereof; 1-5 parts of a processing aid, 0.1-0.5 parts of a film slipping agent and 0.5-3.0 parts of a film anti-blocking agent. The preparation method comprises the following steps: mixing the components according to the parts by weight, extruding the mixture to form pellets after mixing, then performing blow molding to form a film, and then preparing various types and sizes of water-soluble shopping bags. The water-soluble shopping bag has higher bearing capacity and cold water solubility, is suitable for use in water-free environment, and dissolves upon contacting water without producing pollution after being used.