The DArk Matter Particle Explorer (DAMPE) is a satellite-borne device for detecting high energy electrons, gamma-rays, protons and heavy-ions in space. The Plastic Scintillator Detector (PSD) is the top-most of the four sub-detectors of DAMPE, which was designed to measure the charge of incident high-energy particles. It also serves as a veto detector for discriminating gamma-rays from charged particles. In this paper, we first introduce the structure and on-orbit operation status of the PSD. The calibration procedures, including the calibration of the pedestal, the dynode ratio, the detector alignment and the energy reconstruction, are then presented. Based on on-orbit data, the preliminary charge spectrum is obtained.