  The Plastic Scintillator Detector (PSD) of the DArk Matter Particle Explorer
(DAMPE) is designed to measure cosmic ray charge (Z) and to act as a veto
detector for gamma-ray identification. In order to fully exploit the charge
identification potential of the PSD and to enhance its capability to identify
the gamma ray events, we develop a PSD detector alignment method. The path
length of a given track in the volume of a PSD bar is derived taking into
account the shift and rotation alignment corrections. By examining energy
spectra of corner-passing events and fully contained events, position shifts
and rotations of all PSD bars are obtained, and found to be on average about
1mm and 0.0015 radian respectively. To validate the alignment method, we
introduce the artificial shifts and rotations of PSD bars in the detector
simulation. These shift and rotation parameters can be recovered successfully
by the alignment procedure. As a result of the PSD alignment procedure, the
charge resolution of the PSD is improved from $4\%$ to $8\%$ depending on the
nuclei.
