A polarized spectroscopy was designed and manufactured based on the laser-produced plasma experiments to diagnose the X-ray polarization of a laser-produced plasma in 0.2-20 nm. The experiment was performed at the 20 J laser facility in Research Center of Laser Fusion, China Academy of Engineering Physics (CAEP). In the experiment, Poly Ethylene Terephthalate(PET) crystals were used as dispersive elements in the two orthogonal directions and the imaging plates with the effective area of 30 mm×80 mm were taken as detectors. The optical paths of the X-ray beam were about 980 mm and 310 mm from the source to the detectors via the PET crystals, respectively. The X-ray spectrum emitted from the aluminum plasmas was recorded by the image plates. It shows that the polarization of the two Al Ⅻ spectra are about 0.123 3 and 0.148 1 after correcting helium resonance and combination spectrum. The experimental results demonstrate that there is anisotropic phenomenon in the laser-produced plasma, and the proposed method is effective to diagnosis of the polarized spectrum of high-temperature plasma.