The depth video obtained by depth camera or depth estimation software is inaccurate, which will affect the compression performance. So, a HEVC-oriented depth video preprocessing algorithm is proposed. Firstly, the edge-mask of depth video is abstracted. Secondly, the depth pixels are classified and spatially smoothened with the aid of edge-mask. Then, spatial smoothened depth video and its associated texture video are used to perform the Temporal Spatial Transform (TST), and the transformed depth video is temporally smoothened with the aid of transformed texture vide so as to enhance its temporal correlation. Finally, the temporal smoothened depth video is processed by the Inverse Temporal Spatial Transform (ITST) to get the final preprocessed depth video. The experimental results show that bit rate is saved by the depth video preprocessing algorithm, ranging from 7.00% to 23.78%, while the proposed preprocessing algorithm keeps the rendering quality of virtual view images.