Abstract: In the current research on ¹³C-labeled compounds breath test of liver function, methacetin-methoxy-¹³C is the most potential substrate. To study a new method for synthesis methacetin-methoxy-¹³C, methanol-¹³C was used as the labeled material, methacetin-methoxy-¹³C was synthesized efficiently through Mitsunobu reaction and functional group modification. The synthesis yield was 63% and the chemical purity was above 99%. At the same time, this method was used to synthesize 4-methoxybenzoic acid-methoxy-¹³C with methanol-¹³C as the labeled material. The synthesis yield was 67% and the chemical purity was above 99%. The new scheme for the synthesis of methacetin-methoxy-¹³C with Mitsunobu reaction as the key reaction could provide a basis for the study of liver function by breath test.