In this paper, the framed mould used in autoclave processing for composite structure forming was optimized considering thermos-elastic stress field. By adopting the finite element (FE) method, the deformation of the framed mould was obtained under thermo-mechanical loading. Through comparing the deformation of the mould surface in X, Y, Z direction from an engineering point of view, it is concluded that in the design of the framed mould one should focus on reducing the deformation in X & Y direction. A thermos-elastic structural topology optimization method was developed to minimize the thermal deformation of the mould surface, leading to the optimal configuration with periodic hollow units. FE analysis of the reconstructed model shows that compared with the original design, the thermal deformation and weight of the optimized result are reduced by 15.92% and 21.32%, respectively, thus demonstrating the validity of the proposed method.