Abstract: A consideriable amount of dredged clays are inevitably produced during dredging of rivers and lakes and construction of ports. A number of unconfined compression tests on solidified soils are performed in connection with the flow-solidification method for dredged clays at high water content. The main influence factors and variation laws of the unconfined compressive strength are analyzed through a lot of laboratory tests. Three types of failure modes of the treated soils are summarized, and the mechanism of an optimum addition content of phosphogypsum as an industrial waste for solidifying treatment is studied. Both the addition content of solidification agent and the initial water content of dredged clays approximately have linear relationship with the unconfined compressive strength of the treated soils, and the relationship between strength and aging exhibits a logarithmic increasing law. Based on the laws derived from laboratory tests, the quantitative relationship between the strength at different ages and the strength at 28 days is established. Finally, a prediction method for the unconfined compressive strength is proposed for the solidified soils of dredged clays with high water content. It is useful for predicting strength of solidified soils from dredged clays in engineering applications.