The relation among electronic structure, chemical bond and properties of TiC-TiB2 composite was studied by the first principle method. The ionic interaction between the ions in the interface of the TiC-TiB2 composite is stronger than that of the inner ions or of the related single phase. There is stronger covalent interaction between the ions in the interface of the TiC-TiB2 composite. There are differences of densities of state (DOS) among of TiC-TiB2 composite and related single phases as the interaction between of TiB2 and TiC phases. The width of DOS for interface Ti 3d is obviously larger than that of corresponding TiB2 or TiC phase, as the interaction between Ti 3d in interface and others is larger than that between Ti 3d in TiB2 or TiC phase and others.