Local precipitation is a precious water resource on the Alxa Desert Plateau of West Inner-Mongolia, Northwest China. The Hydrogen and oxygen isotope compositions in the precipitation of this region were investigated during 2013 and 2015 to explore the influences on precipitation isotopes and to reveal the moisture source of precipitation. The results show that: (a)δD and δ¹⁸O values in the precipitation show a distinct seasonal variation, with higher values in summer and lower values in winter, on the Alxa Desert Plateau. (b)Among main meteorological parameters(precipitation amount, air temperature, atmospheric humidity and wind speed), air temperature is the most predominant factor controlling isotopic compositions of precipitation on both daily and monthly scales. The local meteoric water line is defined by the relationship between δD and δ¹⁸O on the Alxa Desert Plateau and has lower slope and intercept than those of surrounding areas, implying stronger non-equilibrium evaporation of raindrops in this region. (c)In combination with the HYSPLT air mass trajectory model, the evidence of precipitation isotopes suggests there was a dominant control of westerly and polar air masses on the Alxa Desert Plateau, and the moisture of local precipitation mainly originated from the north and west throughout all the year.