Abstract: 3'-deoxy-3'-18F-fluorothymidine (¹⁸F-FLT) was prepared from N-BOC precursor to improve the synthesis yield, chemical purity and radiochemical purity of ¹⁸F-FLT by home-made automated synthesis module. The results showed that residual water in synthesis system and the amount of precursor could affect the synthesis yield dramatically. The more the amount of precursor, the higher the synthesis yield between 10 mg to 30 mg of N-BOC. The residual water can decrease the synthesis yield. In the presence of excess base, the precursor was consumed by elimination before substitution was completed. When the precursor to base was optimal in 1 to 1, an overall 18F-FLT yield of 26.3% was achieved when the precursor amount was 20 mg（n=20）. The balance of semi-preparatiove HPLC Column can affect purified the final ¹⁸F-FLT product. The chemical purity of ¹⁸F-FLT could be decreased with 8% EtOH as mobile phase in semi-preparatiove HPLC. The high chemical purity, radiochemical purity and synthesis yield could be abtained by optimized the parameter of synthesis with home-made automated synthesis module.