The effect of electron screening on prompt explosion energy of supernova is discussed in regard to progenitor model WS15M⊙. The average heavy nuclei model is used for calculating the electron capture rates. The simulation results show that electron capture rate is decreased and the collapsing time-scale is prolonged by the electron screening, and the total energy of neutrino leakage increases. Acordingly, by the energy of the shock wave also decreases appreciably. The effect of electron screening on other supernova simulations is estimated.