Abstract: Laser Absorption Spectroscopy technology is a convenient and rapid method for the simultaneous determination of hydrogen and oxygen isotope ratios in environmental water samples. This method has been widely used in the environment, geology, ecology, and energy fields due to its simplicity, high detection efficiency, and portability. However, no national standards are available for this method and thus the analytical results are not traceable effectively. Moreover, the use of this method lacks norms and unity. In order to evaluate the accuracy and precision of the Laser Absorption Spectroscopy method for the determination of δD, δ¹⁸O, D/H and ¹⁸O/¹⁶O values of eight water samples (δD value of within -189.1‰-0.4‰, δ¹⁸O value of within -24.52‰-0.32‰), values were determined by 12 laboratories using optical cavity enhanced absorption spectroscopy. Data from each collaboration laboratory is accurate, stable, and reproducible. The precision value of δD is 0.4‰ (1σ) and δ¹⁸O is 0.05‰ (1σ), comparable to the traditional mass spectrometry method. Therefore, the method is suitable for the on-line and real-time determination of hydrogen and oxygen isotope ratio in the field. This study provides a reference for the development and application of the standard method for determination of δD and δ¹⁸O isotopes in environmental water.