The oceans contain hundreds of times more uranium than terrestrial ores. Fiber‐based adsorption is considered to be the most promising method to realize the industrialization of uranium extraction from seawater. In this work, a pre‐amidoximation with a blow spinning strategy is developed for mass production of poly(imide dioxime) nanofiber (PIDO NF) adsorbents with many chelating sites, excellent hydrophilicity, 3D porous architecture, and good mechanical properties. The structural evidences from ¹³C NMR spectra confirm that the main functional group responsible for the uranyl binding is not “amidoxime” but cyclic “imidedioxime.” The uranium adsorption capacity of the PIDO NF adsorbent reaches 951 mg‐U per g‐Ads in uranium (8 ppm) spiked natural seawater. An average adsorption capacity of 8.7 mg‐U per g‐Ads is obtained after 56 d of exposure in natural seawater via a flow‐through column system. Moreover, up to 98.5% of the adsorbed uranium can be rapidly eluted out and the adsorbent can be regenerated and reused for over eight cycles of adsorption–desorption. This new blow spun PIDO nanofabric shows great potential as a new generation adsorbent for uranium extraction from seawater.