Abstract: Through designing different drainage tank the paper studied different drainage conditions and time effects on structural strength formation of soft dredger fill, and carried out grey prediction. The test results showed that when the drainage paths didn’t block, the free water of the soil was fully discharged, the structural strength formation was faster. In the same drainage conditions, the structure strength grows correspondingly with the time, faster in the early, later stabilized. Grey prediction can be used to predict structural strength formation of soft dredger fill in short-time, it gives reference to engineering practice.