Abstract: ¹¹C-MET was synthesized by the solid phase reaction of ¹¹CH₃I and precursor L-homocysteine, and the radiochemical purity of ¹¹C-MET was analyzed by HPLC, ¹¹C-methanol and ¹¹C-methyl iodide were prepared and analyzed, respectively. The primary impurity of the product were analyzed. The influence on the quality of product was investigated by changing the concentration of sodium hydroxide solution and the solvent of dissolving precursor. The results showed that ¹¹C-MET with higher yield and good radiochemical purity would obtain by using 0.1 mL 2 mol/L NaOH to dissolve the precursor, then injecting it into the C18 column after blending 0.1 mL ethanol.