In order to diagnose the polarization of the x-ray line emission of plasmas excited by Z-pinch,a X-ray line polarization spectrometer is developed for measuring the spectrums.With Mica(002) crystal as dispersive element,Bragg angle is in the range of 30°～60°.X-ray lines radiated by plasma are measured in the vertical and horizontal directions,respectively.The X-ray spectra of lines in Ar XVⅡare photographed by using the polarization spectrometer with X-ray film on Yang accelerator.We obtain the resonance line w,the magnetic quadrupole M2 line,the intercombination line y and the forbidden line z in the vertical and horizontal directions.The experimental spectra recorded by the spectrometer are apparently different in the vertical and horizontal directions.The degree of polarization of lines w,x,y and z is calculated to show anisotropic property and the presence of beams in Z-pinch plasmas.