Abstract: To study the stability of ¹⁸F-FDG with routinely synthesis at high radio-dose and high radioconcentration, ¹⁸F-FDG was added 0.1% ethanol or repurification by solid-phase extraction for radiolytic ¹⁸F-FDG to improve its radiochemical purity (RCP). The results showed that the RCP declined from 99% to 95% within 4 h at 6 TBq/L for room temperature(RT). The radiolysis could be depressed with 0.1% ethanol, the RCP could be over 95% even if the radioactivity concentration was 7.4 TBq/L at RT for 6 h. The repurification method could improve the RCP of ¹⁸F-FDG from 80% to 99%. Micro PET/CT imagings of normal rats showed that the vertebra had high uptake with radiolytic ¹⁸F-FDG because of impurity. There were no radioactivity uptaking in bone with repuification of ¹⁸F-FDG. It indicated that 0.1% ethanol could be used as stabilizers for ¹⁸F-FDG to improve the RCP when ¹⁸F-FDG had high radiodose and high radioconcentrtion. The radiolytic ¹⁸F-FDG could be repurified by solidphase extraction to remove the radioimpurity. The method of added 0.1% thanot could be combined with repurification method to assure the RCP of ¹⁸F-FDG for over 95% at any given time andradiodose or contcentrayion.