Abstract: The detection of SF₆ and its substitute gas decomposition components is an important means to evaluate the insulation status of high-voltage electrical equipment. Consequently, the SF₆ decomposition component is taken as an example to carry out literature researches, the concentration distribution of characteristic decomposition components under different conditions is summarized, and suggestions on the detection range and lower detection limit of components are put forward. In addition, detection methods of SF₆ and its substitute gas decomposition products based on optics are reviewed, including emission spectroscopy, direct and indirect absorption spectroscopy. Compared with traditional methods, most methods simultaneously compromise high performance in detection speed, accuracy and sensitivity, and the detection lower limit is usually as low as 10⁻⁶ level. Thus, optical methods have the potential for online monitoring of high-voltage electrical equipment, which is worthy of further research. At present, it is difficult for a single detection method to realize the full component detection of SF₆ and its substitute gas decomposition products, therefore, in the future, an online integrated system based on optical detection and supplemented by non-optical detection will be considered according to different detection demand scenarios.