Thiophene was refluxed with carbon tetrachloride and methanol or ethanol to give dimethyl thiophene-2, 5-dicarboxylate (1a) or diethyl thiophene-2, 5-dicarboxylate (1b) using Ferrous acetate as catalyst. The optimum conditions were n (thiophene)：n (carbon tetrachloride)：n (ferrous acetate)＝1: 2.5: 0.01 and reflux time 6 h in excess alcohol. Yields of thiophene-2, 5-dicarboxylate were 91.5%~95.2%. Compound 1a or 1b was hydrated in base condition and then acidified to give thiophene-2, 5-dicarboxylic acid (2). The optimal reaction conditions were n (thiophene-2, 5-dicarboxylate): n (sodium hydroxide)=1: 2.5 and reflux time 5 h in methanol and water (1: 2). Yields of thiophene-2, 5-dicarboxylic acid were 90.5%~92.0%.