In order to realize the comprehensive utilization of marine sludge, carbide slag (CS) and blast furnace slag (BFS). The BFS produced by the environmental protection treatment of industrial solid waste by alkaline excitation method is mixed with the marine sludge of engineering waste, and then the mixed system is modified by carbide slag, cement and other curing agents. Based on a series of indoor unconfined compressive strength(UCS) tests, X-ray diffraction(XRD) tests and thermogravimetric(TG) tests, the mechanism of solidifying marine silt using carbide slag activated BFS was investigated. The results show that the UCS of the solidified marine sludge initially increased and subsequently decreased with increasing carbide slag ratio and BFS ratio. The optimal mix proportion for modified marine silt was determined to be 15% cement, 6% carbide slag, and 4% BFS. The calcium hydroxide in the carbide slag neutralizes the sulfates in the marine silt, creating an alkaline environment for the solidification reaction. The pozzolanic reaction and carbonization reaction occur in the mixed system. Hydration products, including C-S-H gel, interact with the raw materials to form a stable structure. Crystals like ettringite filled the pores within the marine silt, so that the new composite material had excellent mechanical properties.