In vacuum-preloading engineering in silt foundations in Lianyungang, we optimized the plan of vacuum preloading according to the characteristics of soft ground. With an in -depth analysis of matters of attention during construction, we determined the main causes for the vacuum degree, i.e. difficult construction due to the characteristics of silt, lack of ensuring the vacuum degree of 80kPa, inaccurate calculation of settlement quantity and vacuum time, ineffective construction management, unqualified construction personnel and materials, etc., based on which, we propose the guarantee measures.