Abstract: Cotton is the main crop in Xinjiang. Studying the depth and proportion of soil water under different salt and fertilizer treatments is of great significance for the rational use of irrigation water and ensuring the increase of cotton yield. Taking "Xinluzao 48" cotton as the research object. The soil with three salt gradients was tested: 3, 6, 9 g·kg^-1（S1, S2, S3）; soil with three fertilization gradients（calculated by nitrogen）: 105, 210, 315 kg·hm^-2（N1, N2, N3）. Based on the method of hydrogen and oxygen isotope tracing, the hydrogen and oxygen isotope composition characteristics of cotton soil water and stem water under film drip irrigation with different salinities and different fertilizer treatments were analyzed, and the proportion of water utilization of each layer of soil by cotton under different treatments was analyzed by IsoSource model. The results showed that under different treatments at each growth stage, the maximum proportion of soil water used by cotton was N1S3（79%） at 0-20 cm at seedling stage, N2S3（57.5%） at 20-40 cm at bud stage, N3S1（63.7%） at 40-60 cm at flowering stage,and N3S1（80.3%） at 40-60 cm at boll opening stage. At seedling stage and bud stage, when the salinity was S1 and S2, the proportion of water use of cotton to 0-40 cm soil gradually decreased with the increase of fertilizer application. When the salt content was S3, the absorption ratio of cotton to 0-40cm soil water was N2S3＞N1S3＞N3S3. The utilization law of 40-60 cm soil water of cotton in flowering and boll opening stages was the same as that of 0-40 cm soil water in the first two growth stages. The conclusion could provide a theoretical basis for scientific irrigation of cotton in arid areas of Xinjiang.