Being characterized by wide beam coverage and short revisit time, taking the MEO as a transmitting platform, and the missile borne Bistatic SAR as a receiver platform, the image can be made in the key areas with a wide range and high mobility. In this paper, the equivalent model of MEO space\|missile borne BiSAR is established based on the space system model, and the slant range model of the transceiver platform is described, which is equivalent to a polynomial model. The slant range error in the aperture time is analyzed to verify the validity of the model. According to the characteristics of the platform, the Doppler characteristics are re\|analyzed, and the two\|dimensional space variation characteristics of the Doppler center frequency and Doppler modulation frequency are obtained. The gradient method is used to calculate the range resolution and azimuth resolution, and analyze their changes with the imaging area. The simulation experiment shows that the resolution in the imaging area is not uniformly affected by the subduction velocity, and the oblique angle of view or the double base configuration should be changed so that the target concerned is located in the area less affected by the velocity.