A three-dimensional (3D) video encoding method, decoding method, and related apparatus is disclosed. The decoding method may include decoding a video bitstream to obtain a single sample flag bit corresponding to a current image block in a current depth map, performing detection on a first adjacent prediction sampling point and a second adjacent prediction sampling point of the current image block in the current depth map if the single sample flag bit obtained by decoding indicates that a decoding mode corresponding to the current image block is a single depth intra-frame mode (SDM), and constructing a sample candidate set according to results of the detection on the first adjacent prediction sampling point and the second adjacent prediction sampling point, where the sample candidate set includes a first index location and a second index location, decoding the video bitstream to obtain a single sample index flag bit corresponding to the current image block.