123I, which is applied for the thyroid and other in vivo kinetic study, has a special role in life sciences. The 159 KeV r-ray from 123I is almost ideally appropriate for the current imaging instrurnentation. Its decay mode (electron capture) and short half-life (13.3 hr) reduced the burden of radiation dose to the patients, and its chemical property makes it easy to synthesize the labelling compounds. In this experiment, the production of 123I via the nuclear reaction 124Te(p,2n)123I with 28 MeV protons was sutdied. TeO, is used as a target material, because it has goad physical properties. The target was prepared with TeO, powder and was rnolten into a ellipsoidal cavity (a=14mm, b=10 mm, 270.8 mg/cm thick) of pure platinum. The irradiation was carried out in the external proton beam with incident energies range from 28 MeV to 22 MeV, and current was 30pA. The loss of TeO, target was significantly reduced by using 4-cooling system in irradiation. The dry distillation method was adopted for the separation of 123I from irradiated target, and when it was kept 5 minutes at 780C, its result was quantitative. The loss of the target material (TeO,) was below 0.2% for each production run and 'I from the dry distillation apparatus was captured with 0. 01 N NaOH in NaI form, then the pH of the solution was adjusted to 7.5-9.0 with HC1/NaOH. The Na123I solution was passed through 0.2pm membrane filter, and sterilized under high pressure and temperature for 30 minutes. The prodvction of 'I is acceptable for clinical application based on the quality of USP XXI.