An anti-biofouling shape-memory composite aerogel includes a unidirectional chitosan aerogel channel, a plant polyphenol coating, and a polyphenol/iron ion chelate. The plant polyphenol coating is evenly distributed on an inner wall of the unidirectional chitosan aerogel channel, and the polyphenol/iron ion chelate is located at a top end of the unidirectional chitosan aerogel channel. The anti-biofouling chitosan-based composite aerogel has an evaporation rate of 1.96 kg·m−2·h−1 at an illumination intensity of 1 kW/m2. The composite aerogel has shape-memory properties, and can quickly restore its original shape in water after extrusion, thereby accelerating the diffusion of substances to complete the modification of inner channels. In this way, desirable anti-biofouling ability is achieved, and excellent structural stability as well as continuous and efficient photothermal water evaporation are guaranteed in a complex water environment.