Abstract: Ground-based radar means microwave imaging radar carried by ground-based platform, which can achieve stable, controllable and repeatable observations. For having the advantages above, it can be applied to long-term observations of slope deformation, urban subsidence, landslides and other areas. However, the basic imaging principle of current ground-based radar is synthetic aperture formed by mechanical movement, which takes a long data acquisition time and is not suitable for fast deformation monitoring. Multi-channel antenna array radar can achieve the focusing along azimuth via electronically switch among elements of antenna array, which is much faster than mechanical scanning and can meet the needs of rapid monitoring. This paper introduces the imaging mode based on antenna array into ground-based radar, which greatly improve the efficiency of data acquisition, meanwhile, the digital beam forming is used in the process of ground based radar data. Firstly, the ground-based radar imaging geometry based on antenna array is established. Then, the paper deduces the digital beam forming algorithm for the geometry and describes the procedure of ground based radar data. Finally, by processing the measured slope data, the paper verifies the imaging geometry and method, meanwhile, the imaging performance is analyzed via the imaging results of corner reflectors.