The identification technology of plastic evidence is very important in forensic sciences. The X-ray energy spectra as a fingerprint of the plastic evidence is proposed to identify non-destructively the plastic evidence. The parallel capillary X-ray lens (PCXRL) is designed, and the X-ray fluorescence spectrometer based on the PCXRL and the laboratory X-ray source is developed to obtain the X-ray energy spectra as the fingerprint of the plastic evidence. The minimum detection limit of this X-ray fluorescence spectrometer is in the range of 1~35 ng/cm2. The diameter and the gain of full beam focused by the PCXRL are 3066 μm and 12.7 at 17.4 keV, respectively. There is a plateau where the distribution of the X-rays is uniform in the center of the focused beam. The diameter and the gain of this plateau is 570 μm and 47.5 at 17.4 keV, respectively. These are helpful to identify efficiently the plastic evidence with various sizes. The PCXRL has potential application in the identification technology for plastic evidence.