The construction of solid-state electrolytes for flexible zinc-air batteries is extremely challenging. A flexible and highly conductive solid electrolyte designed with a “seaweed structure” is reported in this work. Sodium alginate serves as the backbone to form a robust network structure, and the grafted quaternary ammoniumgroups provide channels for rapid ion transport, achieving excellent flexibility and hydroxide conductivity. The conductivity of the modified electrolyte membrane (QASA) is 5.23 × 10−2 S cm−1 at room temperature and reaches up to 8.51 × 10−2 S cm−1 at 75 °C. In the QASA based battery, bending at any angle is realized, and the power density is up to 57.28 mW cm−2. This work provides a new way to prepare high conductivity, green solid-state zinc-air batteries, and opens up a research line of thought for flexible energy storage materials.