LGR's ultra water vapor isotope analyzer (hereinafter referred to as UWVIA) is a device capable of continuously measuring the δ2H, δ18O and H2O mole fractions in situ at high frequency under a wide range of varying water vapor concentrations. The high-frequency measurement of water-isotope in the atmosphere-vegetation interface layer provides convenience for researchers to understand water vapor flux at the ecosystem scale, and is of great significance for fitting water vapor movement and predicting climate change. LGR has also designed a water vapor isotope standard gas generator to achieve long-term unattended measurement of water vapor isotope.