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 Sr2+ binding with alginate molecule chain. For both fibers, the more crosslinking sites of Sr2+ with alginate molecule were illustrated in comparison with that of Ca2+. The more robust mechanical performance of Sr‐alginate fibers than Ca‐alginate counterpart was a strong indication of the more strong binding of Sr2+ with alginate molecular chain. FTIR and electric conductivity disclosed the chelation type of Sr2+ with alginate macromolecule being similar to that of Ca2+, which was core‐shell of the analogous “egg‐box” structure. Circular dichroism spectroscopy further certified the extra coordination sites for Sr2+ with alginate molecule than Ca2+. Research on the coordination model will be more beneficial to optimizing the physicochemical properties of alginate fibers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48571.