Distinguishing the absorption spectra of isomers is a global challenge, and early methods of detection could not adequately meet the demand. Using infrared spectroscopy is rapid and simple, requiring low technical skills and is easy to perform on-demand tests, but it performs poorly in terms of sensitivity and accuracy. In contrast, molecular spectroscopy analysis offers robust performance but requires multi-step sample preparation, complex detections, long turnaround times, and a lab-based environment. Clearly, there is a need for an absorption spectroscopy detection method for isomers that is portable, requires low technical expertise, and can quickly provide samples to obtain results. This study conducted an in-depth analysis of the THz absorption spectra of dihydrouracil (DHU) and glycine anhydride (GAH) in the frequency range of 0.3-2.0 THz using Terahertz Time-Domain Spectroscopy (THz-TDS). Combine the experimental THz spectral data with theoretical calculation results. THz-TDS was used to obtain the THz absorption spectra of DHU and GAH, and theoretical calculations were performed using Density Functional Theory (DFT), specifically on the Gaussian 16 computational platform using the B3LYP functional and the 6-311G (d, p) basis set. To analyze the THz wave absorption characteristics of DHU and GAH, the potential energy distribution (PED) analysis method was employed to describe the vibrational modes of the absorption peaks, and the energy decomposition analysis based on forcefield (EDA-FF) was used to analyze the weak interaction energies between DHU and GAH. Theoretical contributions of characteristic absorption peaks of DHU and GAH were explained through Electrostatic Potential (ESP) and Van der Waals (vdW) potential distribution analyses. The electromagnetic properties of THz waves enable them to penetrate various materials while being highly sensitive to organic molecules. THz spectroscopy not only holds potential in studying weak molecular interactions but has also proven to be an effective method in identifying biomolecules with similar molecular structures. This study successfully distinguishes between the two isomers, DHU and GAH, providing an important theoretical and experimental basis for the in-depth exploration of other isomeric molecule designs and functions in the future.