Ultrafine Ti(C,N)-based cermet was sintered by SPS from 1050°C to 1450°C and its sintering properties, such as porosity, mechanical properties and phase transformation, were investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimeter (DSC). It is found that the spark plasma sintering properties of Ti(C,N)-based cermet differ from those of conventional vacuum sintering. The liquid phase appearance is at least lower by 150°C than that in vacuum sintering. The porosity decreases sharply below 1 200°C and reaches minimum at 1 200°C, and afterwards it almost keeps invariable and no longer increases. SPS remarkably accelerates the phase transformation of Ti(C,N)-based cermet and it has a powerful ability to remove oxides in Ti(C,N)-based cermets. Above 1 350°C, denitrification occurred. Fresh graphite phase formed above 1 430°C. Both the porosity and graphite are responsible for the poor TRS.