Abstract: Hydrogen and oxygen isotopic compositions of sediment-bound water, and the product of water-rock interaction, have an important significance to the study of palaeoclimate and palaeoenvironmental evolution.In this study, combined thermogravimetry, vacuum extraction and liquid water isotopic analysis technology are used to extract different sediment-bound water in the weathering profile sediments of hunan, and analyze their hydrogen and oxygen isotopes.Based on the thermogravimetric data, four temperature intervals are determined, 0-120℃, 120-300℃, 300-600℃ and 600-900℃.The host characteristics of water at the temperature intervals of 120-300℃ and 300-600℃ cannot be constrained.The water at 0-120℃and 600-900℃ is determined as absorbed water and structural water.The water extracted from 0-120℃ is termed as absorbed water, which is mainly sourced from atmospheric precipitation after evaporation.As a result of isotopic equilibrium fractionation, the tighter the relationship between sediment-bound water and crystal structure, the more negative the relationship for hydrogen isotopic composition, and the more positive for oxygen isotopic composition.This method can provide valuable information for the study of earth surface processes and hydrological cycles.