Abstract: With the vigorous development of underground space, the ground settlement caused by dewatering has an impact on the stability of surrounding buildings and underground piping systems, which has attracted attentions of domestic and foreign scholars. This article uses typical silt of Wuhan to carry out dehydration process of SWCC test with the pressure plate apparatus. The following results are obtained: SWCC of unsaturated soil; mass moisture content, the axial displacement variation with the change of matric suction and their error correction; water and axial displacement variation with time under different matric suction. According to the measured curve, the water content of the unsaturated soil is reduced with the increasing matric suction before it reaches the residual moisture content; the soil shrinks because of water loss. The axial displacement increases with the increasing matric suction.,at a residual moisture content, axial displacement increase stops changing. During pressurization, axial deformation appears, accompanied by a certain degree of radial deformation. In addition, a detailed analysis is carried out about the instrument itself and the error that may occur during the test, which provides a reference to the pressure plate test.