Abstract: Based on the understanding that the dissolution of soluble salt is the root cause of salt collapsible deformation, three kinds of loess compression tests are carried out on undisturbed Ili loess samples with different NaCl contents, namely, original water content, soaked in pure water and saturated NaCl solution, which is an extension of loess collapsibility test. The difference between water collapse and salt collapse is achieved, and the influences of NaCl content on the characteristics of compression, water collapsibility and salt collapsibility are investigated. The results show that the above three kinds of tests can well distinguish the water collapse and salt collapse. When the NaCl content is small, the water collapse is greater, and with the increase of NaCl content, the leading role of deformation is gradually changed from the water effect to the salt effect. When the NaCl content is about 10 g/kg, the two effects are almost equal. With the increase of NaCl content, the peak salt collapse coefficient increases as a power function, while the peak water collapse coefficient decreases linearly and the starting pressure of salt collapse decreases exponentially. When the vertical pressure is applied, the height of the sample decreases from steeply to slowly, the time of deformation stabilization increases with the increase of vertical pressure.