Abstract: Polydimethylsilane (PDMS) samples were irradiated by electron beam (EB) in vacuum at room temperature, and the relationship between its structure and absorbed dose was investigated. The result of GC-MS reveals that a small amount of H₂and CH₄is released. FT-IR, Raman spectra and XRD curves show that the chemical and crystal structure of PDMS are not changed after irradiated with extremely high dose of several MGy. These results indicate that the radiation tolerance of PDMS is excellent, which might be caused by the delocalized σ electron of the highly ordered Si—Si skeletons.