Synthetic Aperture Radar (SAR) imaging from low altitude aerial vehicles has been gaining much importance together with the widespread use of Unmanned Aerial Vehicles (UAVs). Relatively shorter distances between the mentioned vehicles and imaged scenes require the consideration of near-field scattering phenomenon. In this paper, authors has focused on the design of a SAR simulator for low altitude vehicles that takes the stated phenomenon into account. The inputs of the simulator are a 3-D complex scene consisting of artificial targets and natural environment constructed by triangular surface meshes and parameters of the SAR system. Scatterer reflectivities are evaluated by utilizing the near-field Physical Optics (PO) method and SAR raw data is generated in time domain. Finally, the simulator processes the raw data and constructs the SAR images via Doppler Beam Sharpening (DBS) algorithm.