|A method for degrading an organism includes steps as follows. A composite structure is provided, wherein the composite structure includes a degradation activity donor and a supporter. The degradation activity donor has a piezoelectric property. The supporter carries the degradation activity donor, wherein the degradation activity donor is completely or partially covered by the supporter. A contacting step is conducted, wherein the composite structure is contacted with a medium. The medium includes at least one organism and water. A degrading step is conducted, wherein a mechanical perturbation is generated in the medium to polarize the degradation activity donor, and a separation of an electron-hole pair is generated for degrading the organism.