In present works, the low cost TiO2 powders were partially introduced to raw mixture as playing roles of both reactant and dilution. The experimental results showed that increasing the ratio of TiO2 to titanium powders up to 70wt%, the combustion synthesis reaction could still proceed by self-sustained mode. Single phase of TiNxC1-x with ultra fine particle size could be prepared by using TiO2 as dilution. Influences of TiO2 addition on phase formation and microstructure of product were also investigated. It was found that the combustion temperature and as-synthesized TiNxC1-x particle size decreased as increasing the amount of TiO2 addition.