Spectroscopic ellipsometry is used to measure the relative amplitude and phase change of linearly polarized light reflected by a material surface, so as to obtain the ellipsometric parameters. The optical properties of a material can be deduced by fitting these parameters. This technique is advantageous for being non-contact, highly sensitive, non-destructive, so it is widely used in physics, chemistry, materials science and microelectronics, etc, being an indispensable optical measurement method. This article first introduces the development history of the technology, and then presents the basic principle of the traditional ellipsometer. According to different measurement principles, ellipsometers can be divided into two types: extinction and photometric. The basic structure, measurement principle and related application of these two different types of ellipsometer are briefly clarified. After comparing these various ellipsometers, their advantages and disadvantages are introduced. At this point, a double Fourier transform infrared ellipsometry system developed by Fudan University is highlighted. Then, according to the basic steps of ellipsometric parameter manipulation, a measurement, modeling and fitting process is introduced. The equations of various optical dispersion models used for parameter fitting are introduced in detail and application examples are illustrated. Finally, the future development direction of spectroscopic ellipsometry is proposed.