During the forming of aramid paper honeycomb sandwich component of aircraft composites in the autoclave, the adhesive layer between honeycomb cells will crack or even be damaged, which will affect the mechanical properties of the parts. The tensile properties, compressive properties, shear properties and thermal properties of aramid paper honeycomb core were obtained by testing. Meanwhile, numerical simulation of thermo-mechanical sequential coupling of the whole honeycomb sandwich component and mechanical simulation of the local core area were carried out by combining the finite element analysis method and the inversion method. The results show that the thermal stress during the forming process will not cause the adhesive layer between honeycomb cells to crack; The difference of pressure difference between honeycomb cells required for adhesive layer’s slight destruction and complete destruction is positively related to the initial normal fracture stress of adhesive layer; When the number of loaded honeycomb cells is less than 20, the pressure difference required for the adhesive layer’s slightly destruction is independent of the number of honeycomb cells, but the pressure difference required for the the adhesive layer’s complete destruction decreases with the increase of the number of loaded cells.