Abstract: A Radio-HPLC method was established for the determination of radiochemical purity in sodium iodide［¹³¹I］ capsules for therapeutic use, and so as to provide reference for the quality control standard of these drugs. The chromatographic column(4.6 mm×250 mm×5 μm) filled with octadecylsilane bonded silica gel was used, and the mobile phase was 5.85 g/L sodium chloride solution(0.65 mL n-octylamine was added and pH was adjusted to 7.0 with dilute phosphoric acid)-acetonitrile(V∶V=20∶1). The detector system was ultraviolet visible spectroscopic detector(detection wavelength is 220 nm) and radioactive flow detector connected in series. The column temperature was 25 ℃, the running time was 40 min, and the flow rate was 1.5 mL/min with isocratic elution. The method can effectively separate iodide［¹³¹I］ compounds from radioactive chemical impurities; the linear ranges of iodide［¹³¹I］ and iodate［¹³¹I］ are 0.19-92.50 GBq/L and 0.15-4.81 GBq/L, the correlation coefficient r are 0.993 and 0.997, respectively; the detection limits of iodide［¹³¹I］ and iodate［¹³¹I］ are 3.21×10^-2 GBq/L and 4.74×10^-2 GBq/L, respectively, the limits of quantification are 9.63×10^-2 GBq/L and 7.91×10^-2 GBq/L, respectively, the recovery is 70.0%-125.0%, and the method has good durability and precision. The Radio-HPLC method is suitable, accurate and reliable for the determination of radiochemical purity in sodium iodide［¹³¹I］ capsules for therapeutic use.