The carbides in the carburized layer of stainless steel (SS)/carbon steel (CS) clad plates are prone to inducing intergranular cracks and reducing the interfacial bonding strength. In this paper, SS/CS clad plates were fabricated by horizontal continuous liquid–solid composite casting (HCLSCC), and the formation mechanism of the interfacial carbides and their effect on the elimination of carbides in the carburized layer were revealed by numerical simulation and thermodynamic calculations. During the HCLSCC process, the cladding interface encountered re-melting and re-solidification after rapid melting and solidification, resulting in liquid–liquid and solid–solid diffusion at the cladding interface, where the atomic ratio of Cr/C (Cr/C) gradually increased. Therefore, strip M7C3and M23C6carbides as well as blocky M23C6carbides formed at the cladding interface in turn and had a coherent relationship with the matrix. The blocky M23C6carbides led to an increase of 240% in the interfacial ferrite strength. The formation of interfacial carbides reduced the difference in C activity between the cladding interface and SS, thus preventing the diffusion of C to SS and inhibiting carbide precipitation in the carburized layer of SS, which was beneficial to improving the interfacial bonding strength.