A depth map enhancement algorithm based on Z-displacement of objects is presented in this paper. Most depth map enhancement algorithms utilize either the spatial or temporal information only. In this paper, information in another dimension, Z-displacement, is utilized to enhance the depth map of videos by estimating the scale change of objects. Our experimental results show that the proposed scale changing detection method has higher accuracy and lower complexity compared with the conventional scale changing detection approaches such as normalized gradient correlation. Based on the estimated scale change, the proposed depth map enhancement corrects the depth map by estimating the Z-displacement of objects in the 3D space. Experimental results demonstrate that better depth maps and visual quality of view synthesis are achieved by the proposed method as compared to the state-of-arts.