Abstract: A new method was used to fabricate the polyacrylonitrile-based activated carbon fiber (PANACF) by the electron beam (EB) pre-irradiation in this paper. The polyacrylonitrile-based fiber (PANF) was irradiated by EB and its accumulated absorbed dose was 160 kGy, and then it was dipped in the 10% KOH solution for 30 min, after that, it was placed into the furnace under nitrogen protection for carbonization at 450 ℃ for 30 min. The analysis result of scanning electron microscope (SEM) shows that the surface of pre-irradiated PANACF appears dense honeycomb structure, which is very different with the un-irradiated PANACF. Moreover, the specific surface area (SSA) of pre-irradiated PANACF is about 9 times larger than the un-irradiated sample’s (SSA was calculated by the BET method). The BJH results reveal that the PANACF prepared by EB pre-irradiation is a novel mesoporous structure, and its pore size distribution is focused on the range from 2 nm to 10 nm. The preliminary research results indicate that the surface morphology of PANACF can be controlling by EB pre-irradiation.