Monte Carlo simulation was used to study the dosimetric characteristics and the yield of contamination electrons, as well as eletron removal efficiency of applying helium and lead-filter. The results showed that most contamination electrons came from accelerator head components and air, and the amount increased with the increment of beam field size and primary photon energy. Instead of air, Helium loading in the accelerator head could significantly reduce the electrons scattering from air, and lead-filter could block the electrons caused by accelerator head components effectively. When both methods were used simutaneously, the majority of electrons could be eliminated. Therefore, employing Helium and lead-filter at the same time is an effective way to reduce the dose delivered on the surface and protect the skin tissue.Cited