In order to study the effect of thermal expansion coefficient of mold materials on the curing deformation of composites， the hot pressing tank curing process of composite parts was focused. To address the problem of thermal curing deformation of composite parts caused by the inconsistency of thermal expansion coefficients between composite forming mold materials and composite parts， the interaction relationship between molds and composite parts was studied， and a theoretical model of mold on the curing deformation of composite parts was derived. A numerical simulation model of the mold temperature field was established using simulation software such as ABAQUS， and the simulation data of mold thermal deformation was compared and analyzed with the experimental data of composite part deformation. The results show that the deformation values at different positions of the mold surface of different materials are independent of the structural characteristics of the surface but are related to the size of the surface. The greater the difference in expansion coefficient between mold materials and composite materials， the greater the deformation of composite parts.