Abstract: The lightning mapping imager equipped on the satellite is a new technique for lightning observation.The lightning imager equipped on the geostationary satellite could map the optical emission from the lightning discharge and locate the flash.The FY-4 geostationary lightning mapping imager could observe lightning activities continuously, and provide for the severe weather forecasting and lightning activity characterization in China.The paper showed the development of observation method and product algorithm of the satellite lightning imager, discussed the instrument and introduced product algorithm of the lightning imager.