Effects of doping single Al, Zn, Cu, Ni, Li, and Zr atoms on interfacial bonding in the 3C-SiC/Mg system were studied using the first-principles method based on density functional theory. The Mulliken charge, overlapping population and density of states of representative Zn and Zr atoms were calculated and analyzed. Results show that the most stable stacking structure of the 3C-SiC/Mg interface model is that 5-layer Mg(0001) is stacked on the 10-layer 3C-SiC(111) surface. Among the six 3C-SiC/Mg model structures, the C-terminated center site model has the largest separation energy, the smallest interfacial spacing and the best interfacial wettability. After doping with Zn atom, Zn and Mg atoms are in the anti-bonding state, resulting in the decrease of the separation work of the 3C-SiC/Mg-Zn system. The decrease of the pseudo-energy gap in the density of states weakens the covalent bond in the 3C-SiC/Mg-Zn system, and this is not conducive to interfacial bonding in the 3C-SiC/Mg-Zn system. After doping with Al, Cu, Ni, Li, and Zr atoms, the separation work of the system increases, and Zr has the best effect on improving the interfacial wettability. After doping with Zr, the anti-bonding state of Mg and Si atoms disappears, and a strong Zr-C covalent bond is formed at the interface between the Zr atom and C atom. The delocalization of the density of states increases, and the bonding ability is enhanced, resulting in a maximum increase in the separation work of the 3C-SiC/Mg-Zr system.