Abstract: This study aims to develop and validate a reliable analytical method for the precise determination of the radiochemical purity(RCP) of ¹⁸FFlorastamin, an ¹⁸F-labeled radiopharmaceutical targeting prostate-specific membrane antigen(PSMA). Accurate RCP assessment is a critical quality control requirement to ensure the safety, diagnostic efficacy, and batch-to-batch consistency of radiopharmaceuticals for clinical use. Therefore, establishing a robust and validated method is essential for supporting its pharmaceutical development and regulatory compliance. A reversed-phase high-performance liquid chromatography(HPLC) method was established. Separation was achieved using a chromatographic column packed with octadecylsilyl-bonded silica gel(ϕ4.6 mm×250 mm, 5 μm particle size). The mobile phase consisted of trifluoroacetic acid(TFA)-water(volume ratio 0.05∶100) solution(mobile phase A) and trifluoroacetic acid-acetonitrile(volume ratio 0.05∶100) solution(mobile phase B), delivered via a gradient elution program. The analysis was performed under the following conditions: column temperature of 25 ℃, injection volume of 20 μL, flow rate of 1.00 mL/min, and a total runtime of 31 minutes. Detection was accomplished using a tandem system comprising a UV-Vis detector set at 220 nm and a radioactive flow detector. The method was rigorously validated according to standard protocols to evaluate its performance. The method provides excellent separation, effectively resolving the main radioactive peak corresponding to ¹⁸FFlorastamin from adjacent radiochemical impurities with a resolution exceeding 1.5. It demonstrates excellent linearity(correlation coefficient r=1.000) across a broad radioactivity concentration range from 0.32 to 172.36 GBq/L. The limit of detection and limit of quantification are determined to be 9.60×10⁻² GBq/L and 3.20×10⁻¹ GBq/L, respectively. All validation parameters, including precision and robustness, meet the accepted analytical requirements, and confirm the method’s reliability and reproducibility. This study successfully establishes a fully validated HPLC method for the determination of RCP of ¹⁸FFlorastamin. The method is specific, linear, precise, and robust. It provides a critical and reliable technical tool for quality control, supports the establishment of official standards and ensures the consistent production of ¹⁸FFlorastamin for clinical application. This methodological framework also offers a valuable reference for the analysis of other similar ¹⁸F-labeled PSMA-targeted radiopharmaceuticals.