For the typical structure of carbon-fiber-reinforced polyimide resin-based composite T-stringer-stiffened panels, the problem of porosity defects forming inside the local skin at the stringer end due to the difficulty of removing volatile components during co-bonding was addressed through material property and defect control research. To remove volatile components before the curing reaction initiated, differential scanning calorimetry (DSC) was used to determine the curing temperature ranges of the adhesive film and prepreg. Viscosity – temperature curve analysis showed that both materials exhibited low viscosity at 290 ℃, enabling volatile removal via pressure application. Thermogravimetric analysis (TGA) revealed volatile release rates of 67.94% and 88.96% for the adhesive film and prepreg at 290 ℃, confirming the effectiveness of applying pressure at this temperature to remove volatile components within the composite system. Based on the analysis of pore defect mechanisms, a defect control strategy involving stringer end chamfering was proposed. Results showed that this approach effectively mitigated fiber buckling and inhibited porosity formation.