基于密度泛函理论，在B3LYP/6-311G（d，p）等级下，对巯基乙酸分子进行几何优化，并在CAM-B3LYP/TZVP理论等级下，计算分子的前20个激发态。首先，计算获得分子的基态信息：当红外光谱波数小于1 856 cm^-1时，分子的主要振动模式为弯曲振动；当红外光谱波数大于1 856 cm^-1时，分子的主要振动模式为伸缩振动。其次，计算分子的前20个激发态，筛选出跃迁概率较大（振子强度大于0.05）的4个电子激发，并绘制紫外光谱图。最后，通过轨道对跃迁判断这4个电子激发的激发类型：S0→S10、S0→S11和S0→S13的激发类型为电荷转移激发； S0→S20的激发类型为局域激发。对巯基乙酸分子结构、光谱和能级特征的理论研究，可为其实验表征、毒理风险评估及降解机制研究提供理论依据。

Based on density functional theory， the geometric optimization of thioglycolic acid molecules was performed at the B3LYP/6-311G（d，p） level， and the first 20 excited states of the molecules were calculated at the CAM-B3LYP/TZVP theoretical level. Firstly， the ground state information of the molecules was calculated and obtained. The results showed that when the center wavenumber of infrared spectrum number was less than 1 856 cm^-1， the main vibrational mode of the molecules was bending vibration； when the center wavenumber of infrared spectrum number was greater than 1 856 cm^-1， the main vibrational mode of the molecules was stretching vibration. Secondly， the first 20 excited states of the molecules were calculated， and four electronic state transitions with high transition probabilities （oscillator strength 0.05） were selected， and ultraviolet-visible spectra were plotted. Finally， the excitation types of these four transitions are determined by orbital pair transitions. the excitation type of S0→S13 was charge transfer excitation； the excitation types of S0→S10 and S0→S11 were charge transfer excitation； the excitation type of S0→S20 was localized excitation. Studying thioglycolic acid， which is harmful to humans， can provide theoretical support for experimental research and provide a theoretical basis for subsequent research on its degradation.