Abstract: Based on the multiphase composite ceramic tool material Al₂O₃ reinforced by SiC and (W,Ti)C particles, the magnitude and the distribution of the residual thermal stress are analyzed in detail with the finite element modeling method. The results show that the residual thermal stress in the multiphase composite ceramic tool material is affected noticeably by the distribution unit models, size and distribution forms of the dispersed phases and their volume fractions. Tensile stress fields are found to exist in the matrix together with the compressive stress fields to different extents and in different ranges. The structure of both tensile and compressive stress fields has close relations with the distribution forms of the dispersed SiC and (W,Ti)C particles. The research here denotes that close relations exist between the residual thermal stress and the microstructure and the mechanical property of the composite ceramic tool material.