In this paper, a forward-looking three-dimensional (3D) imaging method based on data-driven approach is proposed. The proposed method adopts a single-input-single-output (SISO) terahertz radar to obtain the one-dimensional range profile of the target. The 3D image is then retrieved from the range profile using the multi-layer perception (MLP) algorithm. Simulations and experiments are carried out to demonstrate the feasibility of the proposed method.