As the first Chinese civilian high-resolution remotesensing satellite, Ziyuan 3 (ZY-3) is equipped with nadir, forward, and backward cameras for stereo mapping. In order to acquire high-resolution mapping accuracy, in-orbit sensor calibration is a particularly crucial procedure after the satellite is launched and orbiting. The key problem of in-orbit sensor calibration is analyzed based on the overall structural design and imaging geometric characteristics of ZY-3. In this paper, a rigorous imaging model of ZY-3 and an interior orientation model are established based on the satellite's designed configuration, charge-coupled device splicing, and imaging characteristics. A new trajectory model, which is called the exterior orientation model, is proposed, which establishes a systematic-error model for the sensors of ZY-3. In addition, the 609th track data are used to validate the new trajectory model, a piece point with a weight polynomial model, which is compared with other trajectory models. Furthermore, different ground control points are selected for the bundle block adjustment experiments with the systematic error and trajectory models of the proposed sensor. It is observed by experiment that the piece point with weight polynomial model has a higher orbit and attitude interpolation accuracy than the other models. For self-calibration with additional parameters, the model can reduce the correlation of the parameters, improve the solved accuracy of the parameters in the exterior and interior orientation models of the ZY-3 sensors, and ensure the correctness and stability of the calibration results.Index Terms-High resolution, in-orbit calibration, piece-point, satellite optical sensor, systematic-error model, trajectory.