  DArk Matter Particle Explorer (DAMPE) is a space-borne apparatus for
detecting the high-energy cosmic-rays like electrons, $\gamma$-rays, protons
and heavy-ions. Plastic Scintillator Detector (PSD) is the top-most
sub-detector of the DAMPE. The PSD is designed to measure the charge of
incident high-energy particles and it also serves as a veto detector for
discriminating $\gamma$-rays from charged particles. In this paper, PSD
on-orbit calibration procedure is described, which includes five steps of
pedestal, dynode correlation, response to minimum-ionizing particles (MIPs),
light attenuation function and energy reconstruction. A method for
reconstructing the charge of incident high energy cosmic-ray particles is
introduced. The detection efficiency of each PSD strip is verified to be above
99.5%, the total efficiency of the PSD for charged particles is above 99.99%.
