The invention relates to the technical field of constructional engineering, and discloses an existing super high-rise building loose pile composite foundation strengthening method. According to the upper structure load requirement, the bearing force of a composite foundation is determined, 1.2-1.5 times of the bearing force during original foundation checking and accepting serves as the bearing force of soil between piles, the design of enhanced bodies in the pile and soil composite foundation is preliminarily conducted, the number of foundation piles in which the enhanced bodies need to be additionally arranged is determined, holes are removed in an existing building foundation or bearing table, the enhanced body foundation piles are constructed in the pile holes, and during enhanced bodyfoundation pile construction, cushion layers are reserved between the pile tops and the foundation or the bearing table. According to the existing super high-rise building loose pile composite foundation strengthening method, the actual bearing force of the existing building foundation is considered, the loose pile composite foundation is formed, the number of enhanced body foundation piles according to a conventional composite foundation design method is reduced, it is guaranteed that the piles and soil jointly bear the loads, stress concentration of the foundation or the bearing table bottom face is reduced, the integral settling volume of the foundation is reduced, the inclination degree of the building is adjusted, a vertical force transmission system of the existing building is not changed, additional stress and deformation are avoided, and safety of the existing building is ensured.