A series of fluxes was employed in a high-temperature reaction to obtain high-afterglow and small-particle-size SrAl2O4 phosphor for fluorescent fiber. Their properties and optical performance were researched through X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), density test, photoluminescence spectroscopy, afterglow test, particle size test, scanning electron microscopy (SEM), and high-resolution SEM measurement. The influence of fluxes on phosphor fluorescent properties was discussed. Results showed that Li2B4O7 had a better fluxing effect than LiF, H3BO3, and Li2CO3 fluxes. Samples with enhanced afterglow intensity and phase purity could be obtained under the synergistic effect of LiF flux. Na+ and Cl− were also researched as alternative options in combination fluxes. Cl− showed a good effect on phosphor luminous properties, whereas Na+ had a negative impact. The fluxing mechanism of combination fluxes was illustrated, and the parameters for preparation technology, including calcination temperature, time, mixing method, and accumulation thickness were optimized.