The invention discloses a quick combined big tree planting method using assisting stump rhizosphere pre-planting. The method includes the steps of firstly, building a planting-assisting stump, pouring the planting-assisting stump with openings in two ends with reinforced concrete, arranging vertical water-permeable pipes in the planting-assisting stump, filling the planting-assisting stump with nutritional soil until the nutritional soil is parallel with the top of the planting-assisting stump, sealing the 1/2-2/3 part, close to the edge, of the top of the planting-assisting stump with cement or a stone slab, wrapping the planting-assisting stump with breathable materials, and the part between the planting-assisting stump and the breathable materials is provided with water-permeable pipes and filled with nutritional soil; secondly, using small tress to make the crown of a big tree, to be more specific, planting multiple small trees at the top of the planting-assisting stump; thirdly, maintaining, to be more specific, keeping the stableness of the small trees, moisturizing the roots the small trees, and controlling diseases and pests. By the method, a combined big tree similar to a 100-year-old big tree in appearance and with the diameter at breast height being above 100cm can be cultured in only 4-5 years, the combined big trees can be fast produced in a large-batch manner, and cost is low.