The terahertz waves are electromagnetic waves with frequencies ranging from 0.1 to 10 THz, exhibiting characteristics of both microwave and infrared, including fingerprint characteristics, coherence, and safety. Due to the weak interactions among most organic macromolecules in substances, the vibrational modes of molecular frameworks, as well as dipole rotation and vibration transitions, often correspond to the terahertz spectral region. Consequently, there has been growing interest in applying terahertz technology within the food industry. This review summarizes the fundamental principles of terahertz spectroscopy for substance detection and highlights recent advances and applications in food analysis. Key applications include harmful contaminant detection, component analysis, quality assessment, and adulteration identification. Additionally, this review discusses current challenges in applying terahertz spectroscopy to food analysis, such as strong water absorption, matrix interference, and the lack of comprehensive spectral databases. Finally, the paper outlines future prospects, including the development of lightweight and cost-effective terahertz sources and detectors for on-site analysis, as well as the integration of terahertz spectroscopy with other modern detection technologies to enhance analytical performance. This work aims to serve as a reference for further research and development of terahertz spectroscopy in the food sector.