Space remote sensing image is developing towards miniaturization, large width and high resolution. Different from the conventional method of push-broom scanning alone the orbit, this paper puts forward a new rotate-broom scanning method using the reflector, which can obtain thousand-kilometers-level width. In this system, combining with the satellite motion model, we analyze the calculation methods of scanning line frequency, resolution and image width. Based on the design parameters, we simulate and analyze the influence on the imaging system when the height of satellite orbit changes. When the height of orbit becomes higher, the resolution is lower, the image width is larger, the transit time is larger, the line frequency is lower, and the design requirement for the back-end readout system is lower. On the contrary, when the height of orbit becomes lower, the resolution is higher, the image width is smaller, the transit time is larger, the line frequency is lower, and the design requirement for the back-end readout system is lower.