Abstract: The resin flow in composite and metal stitched sandwich structure during resin transfer molding (RTM) process was simulated. First, the permeability of fabric and holes of stitched sandwich structure was obtained respectively through the experiment and numerical calculation. Then, the two-dimensional and three-dimensional simplified models that can reflect the flow in holes were established to simulate the resin flow in RTM process. The influence of different process parameters on molding process was discussed. Finally, a molding experiment was made to verify the simulation results. When the ratio of the suture diameter to the hole diameter is within 0.3-0.8, the permeability of the holes decreases with the increasing diameter of the suture. The difference between the permeability of the fabric and the holes is two orders of magnitude. Dry spots are easily produced in holes, so the inlets and outlets should be set to ensure the resin flow through the holes from one side of the core layer to the other side. The area with no defects increases with the increasing injection pressure and decreases with the increasing holes pacing and thickness of the core layer. The unidirectional slotting along each row of holes on core layer can improve the infiltration quality in the holes. When the inlet is a line, the flow of the resin is good. And when the inlet is a point, setting the inlet to the corner can reduce the dry spots on the surface.