A surface extraction method that includes the steps outlined below is provided. (A) Raw input depth data of 3D child nodes are received that includes positions and distances of first 3D child nodes and positions of second 3D child nodes. (B) The neighboring 3D child nodes are grouped into 3D parent nodes. (C) For each 3D parent nodes, propagated distances of the second 3D child nodes are generated. (D) The 3D parent nodes are treated as the 3D child nodes to perform the steps (B)-(D) to generate a tree including a plurality levels of nodes such that a surface extraction processing is performed on the tree to extract at least one surface of the scene.