Abstract: Dissolution of carbonitride in high-strength steel containing Ti and Nb was investigated by means of phase analysis and X-ray diffraction. The results show that the precipitation phases are fcc Ti(CN), (TiNb) (CN) and TiC when heated to 1250℃ without soaking; but mainly Ti(CN) and TiC when heated to 1250℃ and preserved for 45 min, their size increased from 300 nm to 323 nm, and the dissolution rates of Ti and Nb were 64.2% and 85.8% respectively. The content of precipitates extracted from the sample soaked for 80 min was almost the same with that for 45 min, whereas the particle size increased. It indicated that the dissolution process was apparently approaching thermodynamic equilibrium.