The effect of non-stoichiometry on the sintering of TiN_x was studied at 1026°-1392°C for x=0.67-0.95. The rate of sintering decreased markedly with decreasing non-stoichiometry in TiN_x. The results were tentatively analysed by the initial stage sintering equation. The diffusion coefficients of rate limiting species of sintering changed orders of magnitude for the region of non-stoichiometry studied. The relation between the defect concentration and the diffusion coefficient of rate limiting species of sintering was discussed. Sintering of TiN_x was suggestedly controlled by the diffusion of nitrogen in the bulk.