Abstract: In spacecraft research and engineering, the study of charge/discharge effects and total dose effects is crucial. However, ground test facilities simulating space electron radiation environments have limitations, such as limited irradiation area and low electron energy. To overcome the limitations of conventional devices, the National Space Science Center (NSSC) of the Chinese Academy of Sciences (CAS) developed the Huairou 5 MeV electron Linear Accelerator (LINAC). This facility provides tunable electron beams (0.5 to 5 MeV), an 800 mm × 800 mm irradiation area, and beam current densities (1 pA/cm² to 1 nA/cm²) under both vacuum and ambient conditions, faithfully simulating the extreme electron environments in MEO and GEO. It enables comprehensive radiation effects testing at multiple scales, from individual components to small satellites. Since 2021, the LINAC has been extensively applied to qualification tests for multiple spacecraft systems, facilitating quantitative evaluation of radiation tolerance. These capabilities offer critical support for optimizing spacecraft electronics design, hardware screening, and on-orbit reliability assurance.