With　the　increasing　health　and　environmental　awareness,　a　growing　demand　for　health-safe　textiles　has　sparked　significant　interest　in　antibacterial　alginate　fibers　loaded　with　silver　nanoparticles　(AgNPs).　However,　the　existing　preparation　methods　suffer　from　issues　such　as　non-eco-friendly　solvents,　process　inefficiency,　and　short-lasting　antibacterial　durability,　limiting　their　applications.　In　this　study,　a　simple,　green,　and　efficient　synthesis　process　for　AgNPs　was　developed　using　the　microfluidic　technology　coupled　with　ultraviolet/thermal　fields,　which　produced　nanoparticles　with　a　uniform　size　(13.0　±　3.2　nm)　and　long-term　stability　(＞4　months).　Based　on　this　method,　a　sodium　alginate-based　spinning　process　was　designed　to　achieve　in　situ　reduction　of　AgNPs　during　fiber　spinning,　with　the　silver　loss　controlled　within　20%,　a　result　seldom　documented　in　the　literature.　Moreover,　this　process　avoided　interference　from　other　reagents　and　ensured　uniform　distribution　of　AgNPs　inside　and　on　the　surface　of　the　fibers.　More　importantly,　the　AgNP-loaded　fibers　exhibited　99.99%　highly　efficient　antibacterial　activity　against　Staphylococcus　aureus　and　Escherichia　coli　with　a　remarkably　low　AgNP　content　of　2000　mg·kg-1.　Even　after　50　washes,　the　antibacterial　effect　was　still　maintained　at　96.88%　and　95.05%,　demonstrating　excellent　long-lasting　antibacterial　performance　and　significant　application　prospects.　©　2025　American　Chemical　Society.