Terahertz （THz） wireless communication system, which exhibits great potential in the future short-range wireless communications, is known to be a kind of ultra-broadband system with high data rates. THz sources, modulators and detectors are key elements in these systems, while in order to maintain high-quality connection, the THz reflectors are also very important. Here, a reflector which is a kind of one-dimensional photonic crystal made of polyvinylidene fluoride （PVDF）/polycarbonate （PC） is studied carefully. According to the refractive indices of materials in the THz range, the reflection coefficients for THz waves are obtained through transfer-matrix method and Fresnel formula calculation. We demonstrate that, in sub-THz waveband, this device shows high performance and wide reflection band. Furthermore, based on the calculation, the research and the design of THz reflectors are also discussed in this article.