In the production processes of food and pharmaceuticals, the identification and differentiation of stereoisomers constitute a crucial and complex issue, particularly when their molecular formulas are identical, but their crystal structures differ. Pyridine dicarboxylic acids serve as key intermediates widely used in pharmaceutical synthesis, where effective discrimination between different isomers is essential due to their varied physical and chemical properties. The technique of terahertz spectroscopy has emerged as a novel approach for detecting stereoisomers, employing high-resolution terahertz time-domain spectrometers to measure 2,3-pyridine dicarboxylic acid, 2,4-pyridine dicarboxylic acid, 2,5-pyridine dicarboxylic acid, 3,4-pyridine dicarboxylic acid, and 3,5-pyridine dicarboxylic acid, revealing their unique terahertz absorption features at different mass fractions. These isomers exhibit distinct absorption characteristics in the terahertz range. Through density functional theory calculations, a comparison between theoretical simulations and experimental measurements has been conducted, elucidating the primary vibrational modes of these compounds, encompassing the torsional vibrations of carboxyl groups and pyridine rings, bond angle bending, and their coupling effects. The research has demonstrated the unique advantages of terahertz spectroscopy in material identification, highlighting its significant differences from infrared spectroscopy. The findings not only offer insights into the terahertz spectral features of pyridine dicarboxylic acid derivatives but also showcase the potential applications of terahertz spectroscopy in the analysis and identification of chemical substances, providing new foundations for the synthesis and discrimination of pharmaceutical intermediates. 〖HJ〗