We set up terahertz time domain spectroscopy (THz-TDS), using femtosecond laser as light source and using photoconductive antennas as emitter. We also use photoconductive antennas and electro-optic sampling to be receiver. When we use photoconductive antennas to be receiver, we detect the signal which the pulse duration is 165 ps. When we use electro-optic sampling to be receiver, we detect the signal which the pulse duration is 1.5 ps, and the spectrum is 4 THz by Fourier transform. We also compare the pulses with different bias voltage and optical power, and the amplitude of radiation field depends on bias voltage and optical power. Final, we put the sample location to the terahertz measurement system. We expect to apply to bio-sensing and inspection of material in the future.