Abstract: To explore whether there is accordance among three determination methods of the radiochemical purity of Tyr ³octreotide(TOC) and folatepenicillin G amidase conjugate(F-PGA), which are both labeled with ¹²⁵I by Iodogen method, the RCP of the labelings are determined by high performance liquid chromatography(HPLC), paper chromatography and trichloroacetic acid(TCA) precipitation, in which four different concentrations of proteins are used to investigate the effect of them on the determination of RCP. It is shown that both HPLC and paper chromatography can separate the labelings from free iodine efficiently, though HPLC is the most precise and reliable method to determinate RCP of such labelings.In TCA precipitation,the RCP measured with 0.2%BSA is the lowest,but those with three other concentrations of the BSA are similar(P＞0.05).When RCP＜10%, the RCP measured with paper chromatography is not different from that with TCA precipitation(P＞0.05), whereas higher than that with HPLC(P＜0.01). When RCP＞10%,the RCP of ¹²⁵ITOC obtained by TCA precipitation is a bit lower than those by two other methods(P＜0.05), but the latters are similar(P＞0.05),and there are no significant differences to determinate the RCP of ¹²⁵I-F-PGA(P＞0.05).The three methods are correlated each other(r=0.996-0.999, P＜0.001).