The invention discloses an installation method of steel reinforcement cages of a mini-pile. A device comprises a crane and a lifting tool. The installation method comprises the following steps that rebars are prefabricated; the lifting tool is lifted and moved to the position above bottom cage set rebars, suspension sleeves on the lifting tool are connected to the bottom cage set rebars in a threaded mode, and the bottom cage set rebars are lifted and moved to the position above a mini-pile hole; the bottoms of the lifted bottom cage set rebars can be flush with each other, a separator is arranged at the bottoms of the rebars, the rebars are bundled together by clamping hoops in a sleeved mode to form the steel reinforcement cages, the steel reinforcement cages are lifted to the interior of the mini-pile hole, separators and the clamping hoops are repeatedly arranged at the interval ranging from 1.6 meters to 2.2 meters for bundling the rebars, and the steel reinforcement cages are downwards placed; steel rods are arranged in a gap located below the clamping hoops on the topmost portion and enable the last steel reinforcement cage to be borne in the mini-pile hole opening, and thebottom cage set rebars and the suspension sleeves are disassembled and separated; and the lifting tool is moved to the next set of rebars, and the operation is repeatedly conducted. The installation method of the steel reinforcement cages of the mini-pile has the advantages that the steel reinforcement cages are downwards placed as the steel reinforcement cages are manufactured, the construction efficiency is high, the installation method is not affected by the site, the lifting mode is flexible, lifting is easy and convenient, operation is safe, and the construction effect is remarkable.