The laser gas analyzer is based on the principle of tunable semiconductor laser absorption spectroscopy (TDLAS) technology. It scans and analyzes the gas absorption spectrum of specific wavelength, and realizes the measurement of gas concentration by combining advanced technologies such as digital lock-in amplifier and long optical path gas chamber As one of the most advanced gas measurement methods in the world, the instrument has the characteristics of high sensitivity, fast response, no interference from background gas and non-contact measurement, which provides a reliable guarantee for accurately reflecting the changes of NH3, HF and HCl.