Abstract: Abstract: In the arid area after long-term drip irrigation, the accumulation of soil salinity in the crop root zone and its farming availability have attracted a lot of attentions and concerns from researchers, which was also an important factor to limit the agricultural production and affect the oasis ecological stability and the sustainable application of drip irrigation. In this paper, we try to reveal the trend of soil salinity evolution in the root zone with the long-term drip irrigation based on a four-year (2009-2012) sentinel surveillance in five typical farmlands of Xinjiang drip irrigation district (Paotai County, Shihezi City, Xinjiang) where the drip irrigation under mulch was applied. The drip irrigation under plastic film in these five cotton fields has been respectively started from 2008, 2006, 2004, 2002, and 1998. And the conditions of these five cotton fields including the soil texture, structure, irrigation and fertilizer regime, cotton variety and planting pattern were basically the same, except their drip irrigation history (2-5, 4-7, 6-9, 8-11 and 12-15 years). Since 2009, the drip irrigation has been carried out and continually run until 2012. Na+, Ca2+, K+, SO42-, Cl-, HCO3- and Mg2+ were the major ions in these fields, and changes of their contents in the root zone inside the film with years of drip irrigation were analyzed. The results indicated that the salt content of the root zone soil (0-60 cm) under the plastic film in the drip irrigation cotton fields decreased along with the increasing year of drip irrigation in Xinjiang arid oasis region under the current irrigation regime. The decrease of total salt content was notable for the 1st-4th years irrigation, while it became slowly during the 5th-7th years with an average salt content less than 5 g/kg in the root zone. The salt content became stable during the 8th-15th years of irrigation and the average salt and Cl- content were respectively less than 3 g/kg and 0.12 g/kg in the root zone. Relative to the uncultivated lands, the desalinization rate of total salts was more than 94%, and Na+ and Cl- contents in the root zone significantly decreased after many years of irrigation. Similar to the total salt content, the Cl- content tended to decrease exponentially as a whole. Na+ and Cl- were the major decreasing ions after long-term drip irrigation as well as Ca2+, SO42- and Mg2+, while other ions (e.g. HCO3-) showed no obvious change with different irrigation histories. The duration of drip irrigation under plastic film had a significant effect on the survival rate and yield of cotton in arid regions, which were 7.1% and 1 279.2 kg/hm2 for 2-years drip irrigation, 60% and 5 250 kg/hm2 for 5-years irrigation, and >90% and 6 500 kg/hm2 for > -years irrigation, respectively. The survival rate could reach more than 80% after 6-years irrigation. Finally, it is found the local irrigation regime is the main reason inducing the decrease of salt content in the root zone, so it is favorable to maintain the existing irrigation regime for the long-term sustainable application of drip irrigation under plastic film. However, the irrigation should be properly reduced to save water during the late flowering, boll setting and boll opening stages.