Abstract: Aiming at the problem of treating waste mud with high water content in engineering, a combined treatment process of composite flocculation and carbonization solidification is proposed. Taking the waste mud from the bored cast-in-place piles of a certain expressway in Henan Province as the research object, a composite flocculant composed of polyaluminium chloride and anionic polyacrylamide was first used in combination with high-molecular water-absorbing resin (SAP) to achieve rapid dewatering of the mud. Then, carbonization and solidification treatment were carried out with MgO, and a systematic study was conducted on the mechanical properties and durability of the treated mud. The results show that the moisture content of the treated mud has decreased from 90% to 34.06%, and it has changed from a flowing state to a plastic state. The optimal carbonization parameters were determined by using the single-factor analysis method. The unconfined compressive strength of the carbonized waste mud reached 427.5 kPa, and the treated waste mud had good durability. Microscopic characterization analysis indicates that its intensity mechanism stems from the multiphase synergistic effect of carbonization products. This process demonstrates significant environmental sustainability advantages in the treatment and resource utilization of waste mud, offering a novel approach to treating waste mud.