In this study, we propose a broadband polarizer based on the “double-split ring” structure of a Dirac semimetal metamaterial. Further, we investigate the influences of the Dirac semimetal Fermi level and the intermediate dielectric thickness on the polarization conversion performance. The results show that the polarization conversion efficiency is 100% at two resonance frequencies of 1.44 THz and 1.95 THz for an intermediate dielectric thickness of 22 μm and a Fermi level of 70 meV. In addition, For a 22 μm thick intermediate dielectric, the two resonant peaks at high and low frequencies show a blue shift as the Dirac semimetal Fermi level increases from 64 meV to 70 meV. Moreover, for a Dirac semimetal Fermi level of 70 meV, as the substrate dielectric thickness increases from 19 μm to 22 μm, the resonant peak at low frequency does not shift, whereas that at high frequency exhibits a red shift.