The object of this work is to study the influence of polarization effect on energy loss of low energy electrons passing through different dielectrics. The average and most probable energy losses of 0.3-1.0 Mev electrons passing through Be, C and Al foil are measured by using Wilson cloud chamber filled with hydrogen. The experimental result indicates that in such energy region the energy loss of electrons passing through dielectrics, possessing large f0-and ρ-value, such as Be and C, is appreciably reduced due to the pola-rizatioa effect. Here f0 is the ratio of the number of conducting electrons to that of total electrons in the dielectrics and ρ is the resistivity of the dielectrics. The experimental value of the energy loss of electrons passing through Be is smaller than the theoretical values given by Helpern and Hall, and by Sternheimer, who have taken into account of the polarization effect; the experimental value of energy loss of electrons passing through C lies between the two theoretical values.