Terahertz(THz) photoconductive antennas(PCAs) are widely used in the detection of broadband pulsed terahertz waves and are important components in THz spectroscopy and imaging systems. Due to its simple structure and ease of fabrication, the dipole photoconductive antenna is the mostly used antenna for THz receivers. The primary specification of THz antennas is the bandwidth. To study the detection bandwidth of PCAs, dipole antennas with the arm length of 10, 50 and 150 μm and a bowtie antenna with the arm length of 178 μm were studied theoretically and experimentally. The results showed that the detection bandwidth decreased with the increase of the antenna arm length, which is consistent with the microwave antenna theory. Further, a commercial electromagnetic field numerical software was used for simulation. The results were in good agreement with the theoretical and experimental results and the model could be able to predict the performance of actual THz PCAs. The simulation can be used to design broadband and high sensitive THz antennas by optimizing structural parameters. The use of a hyper-hemispherical silicon substrate lens on the back of the receivers was also studied.