The pyroelectric effect, the primary and secondary pyroelectric coefficients were strictly defined. The pyroelectic properties of different materials including single crystals such as TGS, LiTaO_3 and LiNbO_3, ceramics such as PZT, PZT95/5 and PbTiO_3 have been comparied. To get high pyroelectric figure of merit, the modified PZT ceramics have been synthesised. The applications of pyroelectric ceramics including infrared detectors, infrared sensors and infrared camera were also briefly described.