Abstract: An on-orbit geometric calibration model is established based on an offset matrix and direction angle model,the corresponding solution is presented in this paper. Similarities and differences between the physical distortion model and direction angle distortion model are analyzed. The direction angle distortion model in a linear push-broom camera is derived from the physical distortion model. Differences between the field central camera and field bias one are analyzed and their direction angle model formulas are separately provided. Control data from the Songshan mountain test field and a HR image from the TH-1 satellite are employed to verify this calibration model and solution. Experiments indicate that stable inner parameters can be obtained by this calibration model and solution method. Between the two calibrated inner results, 95 percent of along-track direction angle difference is less than 0.1 pixels and 93 percent of across-track direction angle difference is less than 0.2 pixels. After on-orbit geometric calibration, image positioning accuracy was significantly improved.