Large-scale and rapid extraction of uranium from seawater are promising for overcoming the challenge of supply interruption to achieve sustainable nuclear energy production. However, existing uranium adsorbents are limited by bacterial contamination or low seawater flux for long-term operation. Inspired by the efficient nutrient absorption by animal small intestine folds, we have developed a continuous 3D intestine-fold-like hierarchical porous uranium adsorbent using a one-step cryo-polymerization technique. It shows 10 times higher uranium adsorption capacity than the same material without the intestine-fold-like structure. The continuous supermacro pores (10–100 μm) in the adsorbent provide rapid flow channels for seawater; the micropores (∼1 μm) in the pore walls provide a Schiff base and amidoxime sites for efficient uranium capture. Its functional and high-strength double network polymer chains show a compressive strength of 1.4–3.3 MPa. Within a period of seven days in natural seawater, the uranium adsorption rate was as high as 0.97 mg (g d)⁻¹. The presence of an antibacterial Schiff base allows the adsorbent to achieve a uranium adsorption amount of 10.45 ± 0.46 mg g⁻¹ after 30 days in natural seawater. Importantly, the cryo-polymerization technique proposed in this work simultaneously achieves the formation of hierarchical pores and is easily scalable for large-area preparation, providing a reliable adsorbent for seawater uranium extraction and contributing to the sustainable development of nuclear energy.