Abstract: Phosphorus-32 is an attractive and widely used radionuclide for a variety of therapeutic applications owing to its favorable nuclear characteristics. 99.999% or above of the nuclear purity of sodium phosphate ³²P oral solution must be achieved in 2015 P.R.C pharmacopoeia. In this manuscript, the process to prepare the sodium phosphate ³²P solution was studied through the nuclear reaction ³¹P (n, γ) ³²P on the high flux engineering test reactor (HFETR). 300 mg of red phosphorus at a thermal neutron flux of 1.1×10¹⁴ n•cm^-2•s^-1 was irradiated for a period of 28 days, and after the sequential treatments of being dissolved in nitric acid, oxidized by hydroperoxide, and neutralized by sodium carbonate solution, a colorless and clear sodium phosphate ³²P solution was obtained at pH 7. The solution was characterized by a nuclear purity being 99.999 9%, specific radioactivity being 2.43×10⁹ Bq/mL, and phosphorus content being 6.13 mg/mL. The sodium phosphate ³²P solution fully meets the requirement of 2015 P.R.C pharmacopoeia and can be used as material to produce sodium ³²P phosphate oral solution.