The stability of sodium cefuroxime has been a major concern since it was invented as a valuable antibiotic. In this study, online attenuated total reflection-fourier transform infrared spectroscopy was applied to monitor the change in supersaturation and optimize the solvent flow rate in antisolvent recrystallization experiments of sodium cefuroxime. The solubility of sodium cefuroxime under various temperatures T, pH values, and solvents was measured and correlated in models. The effect of the antisolvent (79.1 % ethanol) flow rate on crystallinity was examined, and the products were analyzed by X-ray diffraction, scanning electron microscopy, and stability test. The results showed that appropriate mean particle size, uniform particle size distribution, and good crystalline state could improve the stability of sodium cefuroxime. The optimum antisolvent flow rate for this recrystallization process under these operating conditions was found to be 2 mL•min −1 .