In free viewpoint video (FVV) system,depth video is the geometric information o f three dimensional scene.It is utilized to render the virtual views.The depth video obtained by the depth estimation algor ithm is not accurate,which deteriorates the quality of virtual views and degrades the compression performance.A depth video preprocessing algorithm based on adaptive window is proposed in this paper to improve depth video compression eff iciency and rendered virtual views quality.Firstly,depth video is classified into discontinuous region,foregroun d region in continuous region and background region in continuous region.Then,object edges are extracted in all regions of the depth video.Finally,the non-edge part in discontinuous region is smoothened by Gaussian filter to reduce the impact of sharp depth transition on virtual vi ew rendering.The non-edge part in continuous region is smoothened by adaptive win dow filter for high compression efficiency.Experimental results show that the proposed algorithm can save encod ing bit rate ranging from 8.33% to 34.39%, while it improves the quality of the rendered virtual views by 0.21dB on averag e.Compared with Silva′s algorithm,the proposed algorithm achieves higher compression performance at low bit rate which is significant for depth video encoding,and keeps better object boundaries in th e rendered virtual views.