A combination method of tree wall is provided, comprising the steps of: removing more than two tree elements that are same species or have close phylogenetic relationship therebetween together with a soil-containing culture pot from a nursery directly cultivating the soil-containing culture pot and the tree elements in a pre-excavated slot or pit splitting a bark of one neighboring surface of each tree element or barks of two combination surface parts at both sides of each tree element removing a partially-cut xylem to form a combination part with a planer part integrally attaching the combination parts of the cut xylems of the tree elements together integrally clamping the barks of the neighboring tree elements together and enabling the xylems and the barks of the two integrally-attached tree elements to mutually heal over and produce vascular tissue so as to integrally connect and grow due to cell proliferation by virtue of self-healing function of an injured plant. With the combination method, an entire tree wall of several tree elements is formed accordingly. Furthermore, a clamping apparatus is utilized to fixedly clamp on the xylems of the combined tree elements for the purpose of maintaining straightness of each tree element in the growth process, and the clamping apparatus is removed from the tree elements when the tree elements reach a certain age, so that a flat tree wall can be obtained. In this combination method, the tree wall constituted by more than two tree elements is designed as one unit, and more than one tree wall unit are planted along a configured wall baseline in accordance with a desired shape to form a wall surface or to surroundingly form a closed-type enclosing wall based on the desired shape. Thus, purposes of environment beautification and carbon reduction can be achieved. For allowing tree roots of each neighboring tree element of the tree wall unit to have sufficient spaces for growth in the future, a distance is kept between the tree
