The invention discloses a construction method and structure for mounting a reverse-construction steel pipe column in a rotary drilled pile hole. The construction method comprises the steps as follows: 1, drilling the pile hole; 2, mounting a reinforced concrete bearing platform; 3, hoisting a pile foundation reinforcement cage; 4, hoisting the steel pipe column; 5, mounting a concrete pouring platform; 6, cleaning the pile hole; 7, adjusting the elevation, the center position and the perpendicularity of the steel pipe column; 8, completing pouring of concrete in a pile foundation and the steel pipe column. The method is simple and practical, the construction period can be shortened, the project cost can be reduced, and the problem that the construction period is longer due to the fact that the pile foundation and the steel pipe column are constructed separately is solved. By the aid of the construction method and structure, the construction period is shortened while the project quality is guaranteed. The construction method and structure have the good social benefit and the good economic benefit. According to the construction method and structure, the high-efficiency construction requirement is met, the construction cost is saved, the project cost is reduced, the problem of continuous construction of rotary drilling and the steel pipe column in basement reverse construction is effectively solved, and the construction method and structure have the wide practicability and the popularization performance.