Sr-alginate and Ca-alginate hydrogel fibers were fabricated via microfluidic spinning technology, and various analytical methods were adopted to characterize fibers and disclose the coordination model of Sr 2+ binding with alginate molecule chain. For both fibers, the more crosslinking sites of Sr 2+ with alginate molecule were illustrated in comparison with that of Ca 2+ . The more robust mechanical performance of Sr-alginate fibers than Ca-alginate counterpart was a strong indication of the more strong binding of Sr 2+ with alginate molecular chain. FTIR and electric conductivity disclosed the chelation type of Sr 2+ with alginate macromolecule being similar to that of Ca 2+ , which was core-shell of the analogous "egg-box" structure. Circular dichroism spectroscopy further certified the extra coordination sites for Sr 2+ with alginate molecule than Ca 2+ . Research on the coordination model will be more beneficial to optimizing the physicochemical properties of alginate fibers.