  By using an average heavy nuclei model, the effects of the electron screening
on electron capture (EC) in core-collapse supernovae are investigated. A
one-dimension code based on the Ws15$M_{\sun}$ progenitor model is utilized to
test the effects of electron screening during the collapsing process. The
results show that, at high densities, the effects of EC on electron capture
becomes significant. During the collapsing stage, the EC rate is decreased, the
collapse timescale is prolonged and the leakage of the neutrino energy is
increased. These effects lead to an appreciable decrease in the initial energy
of the bounce shock wave. The effects of electron screeening in the other
progenitor models are also discussed.
