A reflective terahertz metamaterial polarization converter is proposed. The polarization converter structural unit is composed of a typical threelayer structure, which consists of two metal layers and a single dielectric layer, and the top metal layer is composed of an open resonant ring and a hollow disk. The results show that the polarization converter can convert the xpolarized wave into a ypolarized wave with a polarization conversion of more than 80% and a working bandwidth of 0.5840~1.3520THz. In addition, the polarization conversion of the polarization converters approaches 100% at 0.6424, 0.9364 and 1.3018THz, respectively. The polarization converter has the advantages of simple structure, easy processing and wideband polarization conversion, and has wide application prospect in terahertz communication and imaging.