Cross-linked polyethylene (XLPE) is widely used as an insulating dielectric for power cables due to its excellent performance. XLPE insulation is manufactured through processes such as triple-layer co-extrusion, crosslinking, and degassing. Increasing the extrusion processing speed can improve the production efficiency. Early studies by our team have shown that increasing the extrusion processing speed can regulate the distribution of the microstructure of XLPE insulation. However, whether it influences the degassing process has not yet been studied. Therefore, this study introduces a novel soaking method to simulate the degassing process of by-products, aiming to explore the relationship between diffusion of acetophenone and crosslinked network. In this study, XLPE cables were fabricated at three different extrusion processing speeds (2, 2.5, and 3 m/min). Taking the axial samples as an example, when the extrusion processing speed increased from 2 to 3 m/min, the load elongation decreased from 57.4% to 40.5%. The diffusion coefficient of acetophenone calculated from the content of infrared spectral absorption peaks at different positions (2, 3 and 4 cm) decreased, reducing from 1.97 to 1.17, from 1.71 to 1.39 and from 1.51 to 1.28, respectively. Furthermore, the results also confirm that the diffusion coefficients of samples in different directions vary. The reason for these changes is that as the extrusion processing speed increases, the crosslinking density and the orientation of molecules in XLPE insulation along the cable axis increases, leading to a decrease in the diffusion rate. This study reveals the relationship between the diffusion of acetophenone and crosslinked network based on extrusion processing speed, providing a theoretical foundation for the development of next-generation high-performance power cables.