Abstract: The accuracy of direct georeferencing by airborne position and orientation system(POS) in WGS 84 coordinate system and in 80 Xi'an geodetic coordinate system is appraised,the height accuracy by using different geoid simulate methods is analyzed,the boresight angle errors of POS system are calibrated and the calibration results in different test fields are discussed.The empirical results have verified that direct georeferencing of aerial photogrammetry based on POS system requires a calibration field with at least 1 XYZ ground control point to eliminate system errors.The accuracy of direct georeferencing is very good in WGS 84 coordinate system.However,it is necessary for getting accurate 3D coordinates of the photogrammetric points to correct height by using geoid simulate in 80' geodetic coordinate system.