Abstract: Based on the techniques of water-soluble mandrel and digital design, the integrated composite wing box was designed and manufactured by the resin transfer molding (RTM) process. The optimized injection pattern and process parameters were determined by the PAM-RTM code and the RTM mould was designed and fabricated from the results of resin flow simulation. According to the fiber overlay design and forming process, the integral composite wing box was manufactured to verify the validity and feasibility of the RTM technique for the integrated wing box.