Terahertz wave has a good ability to identify biomolecules due to its fingerprint spectrum characteristics. However, the minimum detectable limit of terahertz technology by the conventional tablet pressing method is on the order of milligrams, which cannot meet the application requirements of low concentration detection in the biomedical field—near or below micrograms. Here, we proposed a method to enhance the detection sensitivity by designing a metamaterial chip with the absorption-induced transparency (AIT) effect, which can enhance the interaction between terahertz waves and biomolecules and lower the detectable limit. Taking 7-methylguanine (7-MG) as an example, based on its terahertz characteristic absorption peak, we designed a split-ring resonator (SRR) metamaterial chip, which has the advantages of high sensitivity, unlabeled detection, fast response and simple measurement. Its quantitative detection limit can reach 6.30 μg, which is about 500 times smaller than that of the traditional tablet pressing method (2.95 mg). In addition, for methylated and unmethylated substances, the chip exhibits different frequency shifts, which also realizes the qualitative identification effectively. These results provide a reference for the rapid and accurate diagnosis of diseases associated with molecular methylation in clinical medicine.