The utility model relates to a forestry protection of trees field, more specifically says and relates to a trunk protection device, and it is good that root soil permeates water air permeability, is favorable to accelerating the growth of trees, and reinforcing root of tree's aesthetic property conveniently cleans, improves the environment to can protect the trunk in order to avoid receive external injury, have the heat preservation effect to trees, be favorable to the growth of trees and the construction of forestry. Be provided with connecting hole I on the layer board I, be provided with spliced pole I on the layer board II, be provided with distribution both sides around trunk protection casing II of spliced pole II and snap ring, II symmetries of a plurality of spliced poles on the trunk protection casing II. The snap ring sets up the lower extreme at trunk protection casing II. I fixed connection of support column is in the bottom of layer board I, and II fixed connection of support column are in the bottom of layer board II, the inside of I cartridge of spliced pole on the layer board II connecting hole I on layer board I. Trunk protection casing I sets up the inboard at layer board II. Trunk protection casing II sets up the inboard at layer board I.