To compensate the image motion of a space camera with large field, a general image motion velocity field model was established by combination of coordinate transformation and attitude dynamics for an off-axis three mirror anastigmat camera. In modelling, the effect of off-axis angles of three-mirror system on the image motion was taken into account, and the formulas of image motion velocity field in the off-axis three-mirror system were derived. By taking a space camera with large field for an example, the distribution characteristics of imaging motion velocity field under three typical imaging attitudes were analyzed. The influence of three axis attitude stability on imaging quality of the satellite was studied. The results indicate that the decline of satellite attitude stability, especially the pitching attitude stability, will lead to the decrease of dynamic Modulation Transfer Function (MTF)of focal plane. And the decrease is more obvious when the integration stages are increased. Moreover, the satellite attitude should be more stable when the camera is imaged in a side rolling with a large angle. For the space camera with 96 integration stages and the reduction of MTF no more than 5%, the satellite three-axis attitude stability should be controlled under 0.001(°)/s. the experiment results confirm the above analysis of satellite stability, verify the accuracy of the proposed image motion velocity field model and provide a reliable basis for the image motion compensation of space cameras with large fields.