SAR（Synthetic Aperture Radar） image simulation has been widely applied in designing and testifying SAR system

SAR image ortho-correction

Radar image interpretation and target recognition and so on.With the development of space-borne SAR

a large amount of needs for space-borne SAR image simulation will arise.This paper firstly discusses the rationale of SAR image simulation from geometric and radiometric characteristics of SAR image

such as Range Doppler（RD） model

backscattering model

and speckle model.Based on the conventional RD model

different backscattering models are applied to simulation for different topographic characteristics

such as alpine terrain or flat terrain.Especially

the need for land cover data is emphasized in the case of flat terrain and Ulaby-Dobson’s backscattering model is used.Besides

speckle simulation is discussed based on SAR image statistical characteristics in order to obtain more realistic SAR image.Then the flow of algorithm is given and several key steps are analyzed.This paper realizes the algorithm of space-borne SAR scene image simulation based on image characteristics.By using the algorithm

tests are performed on alpine terrain in Xinjiang and flat terrain in Tianjin.The results prove the efficiency and validity of the algorithm.