  The Forbush Decrease (FD) represents the rapid decrease of the intensities of
charged particles accompanied with the coronal mass ejections (CMEs) or
high-speed streams from coronal holes. It has been mainly explored with
ground-based neutron monitors network which indirectly measure the integrated
intensities of all species of cosmic rays by counting secondary neutrons
produced from interaction between atmosphere atoms and cosmic rays. The
space-based experiments can resolve the species of particles but the energy
ranges are limited by the relative small acceptances except for the most
abundant particles like protons and helium. Therefore, the FD of cosmic ray
electrons and positrons have just been investigated by the PAMELA experiment in
the low energy range ($<5$ GeV) with limited statistics. In this paper, we
study the FD event occurred in September, 2017, with the electron and positron
data recorded by the Dark Matter Particle Explorer. The evolution of the FDs
from 2 GeV to 20 GeV with a time resolution of 6 hours are given. We observe
two solar energetic particle events in the time profile of the intensity of
cosmic rays, the earlier and weak one has not been shown in the neutron monitor
data. Furthermore, both the amplitude and recovery time of fluxes of electrons
and positrons show clear energy-dependence, which is important in probing the
disturbances of the interplanetary environment by the coronal mass ejections.
