Terahertz(THz) radiation from femtosecond photo-induced gas plasmas was explored. Given that THz wave is of great importance in safety inspection and national defense, it was summarized and analyzed that physical mechanism, which covers theory model, polarization characteristic and angle distribution of far field, and control technologies consisting of control of THz intensity, polarization and waveform to meet application requirements was discussed. It shows that there are many ways to generate, explain and control THz radiation from laser-induced plasmas. Among them theory models mainly include four wave mixing model and photocurrent model, and high energy of THz emission could be radiated from two-color femtosecond laser-induced filament in air or generated in laser-induced air plasma on the external electric field.