Abstract: The international energy technology revolution is considered as the main way of reducing carbon emissions, and most countries in the world have been or are formulating carbon neutral plan. Hydrogen energy has multiple advantages, such as source variety, high energy density, terminal zero row, and wide range of use. It is of great significance in protecting national energy security, improving the atmospheric environment quality, and promoting energy industrial upgrading. This paper reviewed optical sensing technologies for hydrogen leak detection, including tunable semiconductor laser absorption spectroscopy technology and palladium-based optical fiber sensing technology. Tunable absorption spectroscopy technology introduced the basic principles of semiconductor laser wavelength scanning and modulation, spectral absorption, second harmonic signal acquisition and gas concentration measurement; taking the latest hydrogen detection technology as an example, discussed the impact of environmental background absorption spectra, the selection principle of target gas fingerprint spectrum and the selection principle of tunable semiconductor laser; and obtained the prototype structure, module unit, test process and test result of the intelligent tunable semiconductor laser absorption spectrum gas concentration detector developed by ourselves. Palladium-based optical fiber sensing technology briefly described the sensing mechanism of metal palladium to hydrogen and the thermodynamic properties of sensing materials; introduced the structure, measurement principle, and measurement principle of various phase modulation, intensity modulation and wavelength modulation optical fiber sensors; discussed the development process of various palladium-based optical fiber sensors; and briefly analyzed the relationship between the sensor's macroscopic performance and microscopic mechanism. Optical detection is non-contact, in line with the safety requirements of hydrogen detection, and has the characteristics of strong selectivity, high sensitivity, and fast response speed.