Abstract: This paper studied and compared the impact of various radiation hardening schemes on the reliability of the AES encryption system, aiming at the problem that SRAM-type FPGAs are vulnerable to soft errors caused by atmospheric neutron irradiation when applied in encryption systems. The experiment was carried out on the atmospheric neutron irradiation spectrometer of the China Spallation Neutron Source. The Xilinx Kintex-7 FPGA was used as the hardware platform, and the neutron irradiation test was carried out on five schemes including unreinforced, error correction code, global clock triple modular redundancy, slice-to-slice isolation triple modular redundancy and hybrid reinforcement. The experimental results show that there are significant differences in the radiation resistance effect and resource overhead of different reinforcement schemes: The hybrid reinforcement scheme has the best radiation resistance performance, and only 3 errors occur under the cumulative fluence of about 3×10⁹ cm⁻². The single particle effect cross section is reduced by 91.8% compared with the unreinforced system, the lookup table resource overhead is increased by about 130%, and the trigger resource is increased by about 10%; The soft error rate of the pure error correction code scheme is reduced by about 33.5%, and the resource consumption is less, but its ability to protect against transient errors in the calculation process is limited; Although the global clock TMR can reduce the soft error rate by 77.13%, the disadvantage is that the hardware overhead and the critical path delay are large; The inter-slice isolation TMR improves the problem of large resource overhead of the global clock TMR, and can be reinforced for sensitive modules. The experimental results also found that neutron irradiation may cause three types of faults such as calculation result error, function interruption and data rollback of the encrypted integrated circuit. The hybrid hardening strategy proposed in this paper combines isolation redundancy and verification mechanism, which not only improves the system’s ability to resist single particle effect, but also provides a feasible solution for the balance between resources, reliability and delay, and has important reference value for the design of high reliability encryption system in radiation environment.