The leakage current characteristics of an insulating sample under high-energy electron beam irradiation are simulated by a numerical model with taking into account the electron scattering, transport, trapping and self-consistent field.The leakage current is measured by using a detection platform. Results show that under the continuous electron beam irradiation, the total electron yield decreases evidently; because of electron transport, the sample near the surface is positively charged weakly and its interior is negatively charged strongly; some electrons are transported downward, forming the electron beam induced current and the leakage current under the long time irradiation. Under the irradiation, the leakage current increases to a stable level gradually. The leakage current decreases with the increase of sample thickness, but it increases with beam energy and current.