Abstract: An useful fluorine-18 labelled intermediate 4-18Ffluorobenzaldehyde was prepared from trimethylammoniumbenzaldehyde triflate and 18Ffluoride and the labeling procedure was optimized by vertical-method. Under the optimized conditions, the synthesis time is 45 min, labeling yields is 62.1%, the radiochemical yield is 56.5% (decay-corrected) and, its radiochemical purity is greater than 95% after purified.