The invention relates to a method for synthesizing 5-N-tert-butyloxycarbonyl-5-N-methylamino-2-thiophenic acid. The method comprises the following steps: obtaining 5-bromo thiophene-2-amine (a compound III) through reduction reaction of 2-bromo-5-nitrothiophene (a compound II), iron powder and ammonium chloride; then obtaining 5-bromo thiophene-2-tert-butyl carbamate (a compound IV) by reacting the compound III with di-tert-butyl dicarbonate; obtaining 5-bromo thiophene-2-(N-methylamino) tert-butyl formate (a compound V) by reacting the compound IV with organic base, methyl iodide or dimethyl sulfate; enabling halogen metal exchange reaction to happen between the compound V and a metal organic reagent under salt bath and nitrogen atmospheres, then using carbon dioxide for replacing nitrogen in a system, and continuously reacting so as to obtain the 5-N-tert-butyloxycarbonyl-5-N-methylamino-2-thiophenic acid. The method has the advantages of short synthetic route, simplicity and convenience to operate, high yield and facilitation of industrialization.