Youjiang River Valley in Baise is one of the famous dry and hot river valleys in China. Drought is the most serious meteorological disaster in the region. It has a unique suitable environment for mango and is the main mango producing area in China. However, the research on the water use strategy of Mango in Baise dry-hot river valley region is still lacking. Based on based on the measuring of hydrogen and oxygen stable isotope of precipitation, soil water at different layers, groundwater, and mango xylem water, the variation characteristics of hydrogen-oxygen isotope an its influencing factors of precipitation were analyzed, and the water absorption sources of mango roots at different growth stages were quantified. The hydrogen-oxygen stable isotopes and d-excess had obvious seasonal changes in the year, which were low in rainy season and high in dry season. The local meteoric water line was δD=8.2587δ¹⁸O+12.308 (r=0.9968, n=35, P<0.001) for the area. Under the influence of monsoon climate, the stable isotope value of precipitation had a significantly negative linear relationship with precipitation amounts and air temperature (P<0.05). During mango flowering stage, young fruit stage, fruit expansion stage, and mature stage, the stable isotopes of soil water became poor with the increase of soil depth. In the flowering stage and young fruit stage, mango trees used a relatively uniform proportion of soil water at different depths and groundwater, while in the expansion stage and maturity stage, mango trees mainly used deep soil water and groundwater, indicating that mango trees in this area mainly use deep soil water and groundwater as water sources, as mango trees' roots are mainly distributed in deep layers, and reveals its conservative water use strategies. The variation of hydrogen-oxygen stable isotopes of precipitation indicates the xerothermic environment of Baise dry-hot river valley region, and mango mainly uses deeper soil water and groundwater, the above results are expected to provide a basis for the sustainable development of mango industry in this area.