To counter the phenomenon of particle aggregation in the process of vacuum preloading treatment in the process of ultra-soft soil,a new type of water absorption,reciprocating water absorption,is put forward to be applied in vacuum preloading reinforcing the ultra-soft soil.With different vacuum degrees of the adjacent vertical drainages (PVD) at the same time,we realize the asynchronous vacuum water absorption of the ultra-soft soil.It is found through the model experiment that the drainage capacity of reciprocating water absorption is 1.1 times of that of regular water absorption.The analysis of mechanism of reciprocating water absorption vacuum reloading method reveals that this method can prevent fine particles from excessive migration and contribute to the consolidation of ultra-soft soil drainage.