Abstract: In this paper the label-ling of four radiopharmaceuticals, 6-Iodocholesterol, o-Iodohippuric acid, Rosebengal and fatty acid is accomplished with hydrothermal melt method. The kinetic of heterogeneous isotopic exchange reaction in hydrothermal melt state is studied and the results show that this labelling methd gives high yield, rapid rate and good purity.