To meet the requirements of positioning accuracy of tridimensional mapping system, based on development of three-linear CCD camera, the practical imaging model of three-linear tridimensional mapping camera was constructed to confirm mathematics formula between the ground point in earth coordinate system and its image point in CCD sensor coordinate system and in uniform image plane coordinate system. Then, the practical error model was deduced to analyze main error source, and integrated positioning accuracy was analyzed according to camera parameter. The results indicated that the positioning accuracy can reach 50 meters under the condition of non-control ground point, meet the requirements of user and verify validity of imaging and error model.