The plastic scintillator strips detector (PSD) consists of one double layer (one x and one y) of scintillating strips detector made of scintillating strips of 1 cm thick, 2.8 cm wide and 82 cm long. The strips are staggered by 0.8 cm in a layer, thus fully covers an area of 82 cm by 82 cm. The PSD serves as anti-coincidence detector for photon identification, as well as charge detector for cosmic rays. The design specification is a position resolution of 6 mm, and a charge resolution of 0.25 for Z = 1 to 20.