The compositions of the core/rim structure and liquid binder of TiC based cermets with nano TiN powders addition have been investigated in order to better understand the influence of compositions on properties. In addition, the distribution behaviour of nano TiN particles and the role of Mo addition were studied respectively. It was found that most of the nano TiN particles were distributed between the TiC/TiC boundaries and the variations in the Mo content had a great influence on the rim growth. Furthermore, a significant improvement in the mechanical properties of TiC-Ni-Co systems was found, compared with that of TiC-Ni systems. The refined microstructure and high fraction of rim phase in the TiC-Ni-Co systems are likely responsible for this difference.