Abstract: Based on the characteristic of collapsibility for saline soil, field tests were carried out in Chaerhan salt lake. In the tests, field double-line method was supplied, and its applicability was verified. According to the data, the law of field collapsibility was acquired, and the relevant technical basis was provided. The tests indicated that double-line method is suitable for the field experimental research on collapsibility. In its process, there exists a normal initial collapsibility pressure and a real one, in which the former (75 kPa) is the beginning of collapsibility, and the latter (110~115 kPa) is the critical point for the exchange of subsidence between natural and flooded foundation, while the subsidence of the foundation is divided into three stages by these two pressures. When the peak collapsibility pressure (175 kPa) reaches, the corresponding coefficient also reaches the maximum, namely the peak collapsibility coefficient (0.194). When the loading exceeds the peak pressure, collapsibility becomes slower, and the coefficients get smaller.