Objective To investigate the microbial disinfection and sterilization effectiveness of an electron linear accelerator on the surface and interior of postal packages, and to design and conduct a penetrating radiation disinfection and sterilization experiment. Methods This experiment selected Bacillus pumilus E601 (ATCC 27142) as the indicator microbial strain for radiation. An experimental model of postal package was subjected to penetrating radiation with different dose gradients using high-energy electron beams generated by an S-band 10 MeV electron linear accelerator. The disinfection and sterilization effectiveness was assessed by culturing and counting B. pumilus after high-energy electron beam radiation treatment. A control group was established to analyze the influence of actual absorbed doses at different gradients on the disinfection and sterilization effectiveness of the electron linear accelerator. Results The actual absorbed doses of high-energy electron-beam radiation required to achieve 1-, 3-, and 6-log reductions of B. pumilus were 1.63, 5.07, and 10.22 kGy, respectively. Complete inactivation was achieved at an absorbed dose of 10.92 kGy, which met the processing requirements specified in the technical standard for ionizing-radiation disinfection. Conclusion The experimental data indicated that the actual absorbed dose for B. pumilus is linearly positively correlated with the log reduction of bacterial colonies killed by electron beam radiation. For disinfection and sterilization requirements in different scenarios, the required actual absorbed dose can be achieved by dynamically adjusting the operating speed of the under-beam transmission system.