Abstract: Based on measured date in field, the soil salt changes for cotton field with drip irrigation under the plastic mulch were investigated. Through analyzing the salinity changes in cotton field with different irrigation years in four different growing period, it was concluded that salt content in soil depth 0-20 cm was reduced during before planting, seedling stage, and the boll opening period, but increased during the blooming-bolling stage. Salt content in 40-80 cm increased slowly during before sowing and reduced during the blooming period and boll opening period. The accumulation of salt at emitter was less than that at any other position but more at interspace of films in horizontal direction. The accumulation of salt in 0-20 cm of vertical direction reducted, but in the 60-100 cm it was larger. Meanwhile with the drip irrigation time extension, soil salt content would increase, especially in the 60-100 cm, the increasing trend was significant. At the location of emitter, inter-lines and inter-films, the total salt content would increase successively. The zone of 60-100 cm was of largest salt accumulation. In the cotton growth period, the depth of 0-60 cm soil kept desalting state, and the depth of 60-100 cm soil appeared depositing salt state. The results can provide references for management and prevention of drip irrigation water and salt under mulch in arid regions.