In this paper, an algorithm based on multiple-input-multiple-output (MIMO) through-wall-radar is proposed to deal with the problem of the ground ghost influence in three-dimensional (3D) down-view imaging for moving target. The 3D back-projection (BP) imaging is utilized to obtain the original image with the information about the target and the ground ghost in down-view imaging mode. Experimental results are provided to explain the cause of ground ghost. According to the focusing delay conversion, a novel algorithm is proposed to suppress the ground ghost. Specifically, first, the cross accumulation and the density-based spatial clustering of applications with noise (DBSCAN) are utilized to extract the range of target and ground ghost, and then the range difference between target and ground ghosts is derived. Next, the focusing delay conversion is employed to acquire a new image in which the position of the ground ghost matches the target. Then, the multiplicative fusion is employed for the converted image and the original image to mitigate the ground ghost. Finally, experimental results are used to validate the effectiveness of the proposed algorithm.