Abstract: A reconnaissance orientating method for mast-mounted photoelectric system was described. Single gyro and a double-axis inclinometer were utilized to substitute for a tri-axis perpendicular gyro, to measure the attitude of the photoelectric equipment. Combined with the earth north orientation by inertial navigation equipment, the relative distance between object and equipment obtained by laser range finder, and the native geodetic coordinate obtained by satellite positioning, the geodetic coordinate of object could be acquired accurately by coordinate transformation.The examination results show that the system orientation accuracy can reach 0.3 mil, and the object positioning accuracy can excel 10 m(CEP).