Metal materials still dominate the separation shell of pyrotechnic separation devices in space launch vehicles. Moreover, research on carbon-fiber–reinforced polymer (CFRP) composites as a separation shell material has mainly focused on the exploration and test stages. Based on safety and environmental adaptability, the buffer substance in separation devices has a great influence on the cutting results of laminates. In this study, compared with the traditional separation device, a new separation device with a shaped charge and buffer substance was designed by finite-element analysis (FEA), and a test was carried out. The predesigned cutting strategies were divided into three categories: no buffer, expansion–deformation energy-absorbing (EDEA) material buffer, and low-density energy-absorbing (LDEA) material buffer as the control group. Based on the separation time of the laminate, delamination of the laminate, deformation of the protective cover, and environmental applicability of the device, the results show that the proposed separation device with LDEA as a buffer is the best, and the trend of delamination is consistent in FEA and the test. The LDEA buffer can effectively reduce the secondary damage of detonation products to the laminate by crushing and absorbing energy to improve the separation effect of the separation shell, providing guidance for the design of CFRP-based separation devices with shaped charges.