Characteristics, classification and hydrogen oxygen compositions of halite fluid inclusion of core sample were used to reconstruct paleo environments during salt deposition of the Thakhek area, Laos, and based on which the way of supply of salt materials was explored. The results show that, primary halite in the Lower Member of the Tagon Formation mainly includes two types, the chevron halite and the cumulate halite. The chevron halite crystals largely occur in the Lower Member of the Tagon Formation, and the cumulate halite crystals is relatively few but usually coexisted with chevron halite crystals in the same layers, indicating an extremely shallow water environment during halite formation. Hydrogen oxygen isotopic compositions of halite fluid inclusion obviously deviated from the global mean meteoric line and mainly concentrated at the bottom right of the line, suggesting a strong evaporative condition during halite deposi tion. The vertical variability of hydrogen oxygen isotope probably implies an increasing trend of air temperature from halite to potash salt deposition. The sea level peaked at the middle Cretaceous. However, water level of salt basin dropped significantly due to continuous subsidence of salt basin and strong evaporation concentration of salt lake, When this occurred, the difference in water level between the sea and salt basin created a horizontal hydrostatic head gradient that had the potential to drive water through the barrier. Moreover, desert sediments occurred widely in Khorat Plateau during the early Cretaceous, providing a necessary passageway for the large scale sea water. Therefore, combining with the existing data, we proposed that, in addition to marine intrusion, seepage of seawater through barrier played a significant role in supplying of salt materials of basin in Laos.