Circuit breaker is a significant equipment to ensure the safety and reliability of the power grid. Gas circuit breakers generate arc when switching currents

which is a high-temperature transient process accompanied by complex physical and chemical reactions in milliseconds. Constrained by this

relatively limited methods can be used in the study of the breaking process

especially the testing of key parameters. In order to construct accurate and reliable arc models and carry out relevant calculations

it is necessary to obtain the behavior mechanism and key microscopic parameters of arc plasma under different conditions. Therefore

it is necessary to discuss the testing techniques of microscopic parameters of the gas arc. Based on the test platform of key parameters of gas arc in XIHARI

this paper discussed the application of schlieren method and emission spectroscopy on arc testing device

introduced the principles and application scope of different test methods and built the corresponding optical test platform. It also provided reference and support for the application of optical testing methods in the study of the arc behavior mechanism in the switching process of gas circuit breaker.