The imaging principles of a three-line stereo mapping camera was analyzed. To overcome the differences of image motion speeds and drift angles of the forward-view camera, nadir-view camera and backward-view camera, the calculation formulas of image motion speeds and drift angles for forward-view, nadir-view and backward-view cameras based on an ellipsoid model were deduced.By taking a three-line stereo mapping for an example and using the WGS84 earth ellipsoid model,the influences of image motion speed matching remains and drift angle remains on the image quality of a three-line stereo mapping camera were analyzed when the forward-view and backward-view cameras both adjust the row transfer periods and drift angles same as the nadir-view camera. Results indicate that with 5% reduction of MTF as a constraint, if more than 2 TDI stages are used nadir-view camera, the forward-view and backward-view cameras should adjust their row transfer periods respectively; However,if drift angles of forward-view and backward-view cameras are adjusted according to nadir-view camera, TDI stages should be no more than 40.