Photoconductive antennas with different structures generate terahertz (THz) waves with different peak frequencies at the
same experimental conditions, so does the same antenna at different experimental conditions. It is necessary to
investigate the determinants of peak frequencies of THz radiation from photoconductive antenna to obtain the THz wave
with required peak frequency. In this paper, the factors of laser spot size, trapping time, carrier lifetime, carrier density,
bias field, antenna gap size were analyzed based on our experiment and literatures. The peak frequency moved to higher
frequency with the decrease of antenna gap size, carrier lifetimes, trapping time, laser beam diameter, and the peak
frequency moved to lower frequency with the decrease of bias field, carrier densities.