An electron beam radiation device for sterilization of the packing box surface was developed successfully at Institute of Modern Physics (IMP), and the reliability test of 8 h was achieved for industrial application. Six electron curtain accelerators were installed in the sterilization transport line for processing the six whole surfaces of the box. This paper introduces the design of the electron curtain accelerator. The E-gun code was used to compute the trajectories of the electron beam, and it is proved valid with experimental results. The high voltage insulating structure is optimized based on CST software to improve the uniformity of the electric field and decrease the numbers of the high voltage breakdown. Finally, the radiation dose distribution was tested and the inhomogeneity is less than 10%, which meets the requirement for the industrial application.