Combined tree pool irrigation system and use method thereof

The invention relates to a system for tree pool irrigation. The system is provided with a water tank and an infiltration pipe. The water tank comprises a first tank body part and a second tank body part. The first box body part is provided with a first outer side edge, a first inner side edge, a first upper end edge and a first lower end edge; the second box body part is provided with a second outer side edge, a second inner side edge, a second upper end edge and a second lower end edge; a first tree hole concave part is arranged in the middle of the first inner side edge of the first box body part, a second tree hole concave part is arranged in the middle of the second inner side edge of the second box body part, and during assembly, the first inner side edge and the second inner side edge are in butt joint, so that a tree hole is defined by the first tree hole concave part and the second tree hole concave part. And an outer contour matched with the inner contour of the tree pool is formed. The water tank is