关于水分子的研究对理论和应用科学都具有重要意义。文章对于水分子结构的光谱研究历程进行了简要介绍，已有的大量光谱学研究及分析涉及多样的研究对象和多种光谱学研究手段。从水分子的转动和振动光谱角度，说明了键角的确定和振动能级等信息。通过对线性光谱（红外光谱等）和非线性光谱（和频谱等）中的例子进行说明，介绍了过往具体研究工作。对于研究HOD/D₂O系统在激发OH伸缩振动后分子内的能量振动弛豫过程，讲述了具有启发性的量子力学研究方法。水蒸气的太赫兹非线性光谱学作为水的光谱分析前沿进展之一，研究观察到太赫兹场中的水蒸气共振处的跃迁吸收随着场强的增加而增加，并用水分子中的阶梯多光子跃迁理论解释了吸收反饱和现象。

The study of water molecules is of great significance to both theoretical and applied science. In this thesis, the history of spectral research on water substructure is briefly introduced. A large number of spectroscopic research and analysis have involved various research objects and various spectroscopic techniques. The determination of bond angle and vibrational energy level are described from the rotational and vibrational spectra of water molecules. Examples of linear and nonlinear spectroscopy (FT-IR and SFG spectra, etc.) are introduced. In this thesis, the proposed inspiring approach to study the vibrational energy relaxation in HOD/D₂O system after excitation of the OH stretch is described. The terahertz nonlinear spectroscopy of water vapor is one of the advances in spectral analysis. It is observed that the absorption at the position of the resonances increases with the THz intensity. The reverse saturation of absorption is explained by stepwise multiphoton transitions in water molecules.