Abstract: The optimization for high synthesis yield was designed with ¹¹C-Triflate-CH₃I as methylation agent for dopamine transporter imaging agent of ¹¹C-β-CFT. The influence factors of the synthesis process were discussed, and the optimum synthetic conditions were established. In the paper, the study showed that the amount of precursor, the irradiation time, eluated condition, the reaction solvent etc could effect the synthetic efficiency. ¹¹C-β-CFT was automatic synthesized on PET-CM-3H-IT-Ⅰ with the optimum process conditions as the irradiation time 10-24 minutes, 0.5-1.0 g/L of precursor in 0.2 mL acetone: acetonitrile(1∶1, V∶V) and room temperature. We obtained a radiochemical yield of (76.93±6.49)% (n=76, ¹¹C-Triflate-CH₃ EOB). The radiochemical purity of final products were over 97%. The specific activities of final products were over （56.26±1.55） TBq/g. It took 16 minutes from ¹¹C-CO₂ to ¹¹C-β-CFT and the radio activity of ¹¹C-β-CFT were (8.07±1.94) GBq (n=76). By optimization of the technological conditions, the target product was suitable for clinical, the synthetic process was reliable and full automated, the product yield was improved and the residual problem of Sep-Pak C18 was resloved.