Abstract: The present disclosure relates to a composition for stabilizing the radiochemical purity of [18F]fluoro-dopa by inhibiting the formation of impurities during a predetermined time period, and a method for preparing the same. The composition according to the present disclosure includes: [18F]fluoro-dopa; ethanol in a concentration of 5% to 30%(v/v) relative to the total composition; and a buffer having a pKa value of 6 to 8.1 at 25° C., in which the composition stabilizes the radiochemical purity of the [18F]fluoro-dopa by inhibiting the formation of impurities during a predetermined time period.