Vacuum preloading is an effective consolidation method to treat thick soft clay.In order to measure the increase of consolidation and the deformation change during the ground improvement,the consolidation process should be monitored.The pore water pressure is an important parameter to indicate the dissipation of excess pore water pressure.Piezometer can be divided into two types,open and sealed respectively.The measuring principles of open and sealed piezometers are analyzed,the performance of vibrating wire piezometer in vacuum preloading is checked by field trial tests,and the methods to improve the long term robustness and accuracy of vibrating wire piezometer are proposed,including adopting filter stone with high air enter value and Ridley-type flushable piezometer.