“This study systematically revealed for the first time the cortical selective mechanism of electron beam irradiation on the radial heterostructure of polyacrylonitrile (PAN) precursor fibers by integrating multiple characterization techniques. Research has confirmed that both irradiated and non irradiated PAN fibers exhibit significant skin core structures, with higher crystallinity, crystal size, and orientation of the (100) crystal plane in the skin layer compared to the core layer; As the absorbed dose increases, the crystallinity of the cortex decreases, the grain size shrinks, and the orientation slightly decreases, while the interplanar spacing remains almost unchanged, and the core structure parameters change very little. The differential evolution between these skin core structures can to some extent enhance oxygen diffusion efficiency, laying the foundation for improving the uniformity of PAN fiber pre oxidation process. Further research has found that there is a synergistic effect between irradiation and heat treatment, with 200 kGy being the optimal absorption dose for cyclization rate, and the reaction degree can reach 62% at a temperature of 250 ℃; And 500 kGy is the optimal radiation absorption dose for carbon yield, with a carbon yield of 50.5% at 1000 ℃ (an increase of 12.25% compared to non irradiated samples). By adjusting the irradiation conditions reasonably, the pre oxidation and carbonization processes of PAN fibers can be optimized, providing new experimental evidence for the preparation of high-performance PAN based carbon fibers.”