Terahertz (THz) waves generation and detection methods based upon ultrafast laser technology are introduced. The detection methods include free-space electro-optic sampling (EO) and air-biased-coherent-detection (ABCD). EO is based upon the electro-optic effect and it can detect THz time waveform by measuring the change of the probe laser polarization. ABCD is an three-order nonlinear optics effect and there is no frequency limitation for ABCD so it can detect broad bandwidth THz pulses. THz generation from photoconductor antenna, optical Dember effect, optical rectification and laser air-plasma interaction are introduced. And the properties of THz generation are discussed. Optics rectification with tilted pump laser pulses front excitation can generate strong THz emission. The THz pulse bandwidths are limited in the former three methods while it is broader from laser air-plasma interaction.