Dredged soil has the disadvantages of high moisture content and low strength, making it unsuitable for practical engineering application. However, a gelling agent system composed of ground granulated blast-furnace slag (GGBS) and carbide slag (CS) can enhance the strength of dredged soil. Additionally, phosphogypsum (PG) can react with the products of this system (calcium silicate hydrate) to form ettringite and improve strength. In this study, CS, GGBS, and PG were selected to solidify dredged soil with high moisture content. The flowability test, unconfined compression test, and direct shear test were employed to evaluate the engineering properties of the dredged soil, while the scanning electron microscope test (SEM), X-ray diffraction test (XRD), nuclear magnetic resonance test (NMR), and toxicity characteristic leaching procedure test (TCLP) to investigate the microstructure evolution of the cured dredged soil. The results indicated that the decreased flowability of cured dredged soil showed a decreasing trend with increased curing agent content. The strength of cured dredged soil increased first and then decreased, and increased finally with the increase of PG content. The optimum PG content was identified as 10 % when the GGBS content was set as 15 %. The internal friction angle of cured dredged soil increased with increased PG content. The change of pore structure and hydration reaction were identified as the main root cause for the change of sample strength. The new cementing material composed of CS, GGBS and PG can effectively resolve the insufficient strength and high water content problems of dredged soil, while having negligible impact on the environment. Moreover, since it is made up of industrial by-products, it has a lower carbon footprint than the traditional cementing materials of lime or cement.