The invention discloses a hoisting method of a reinforcement cage of an extra-deep diaphragm wall. The hoisting method comprises the following steps that before the reinforcement cage is hoisted, first hoisting points and second hoisting points are reinforced by trusses; the reinforcement cage is hoisted by a main crane and an auxiliary crane, a lifting hook of the main crane cooperates with a horizontal shoulder pole to hoist the reinforcement cage, the reinforcement cage is hoisted straightly by a hoisting device, and the main crane and the auxiliary crane are used for hoisting the reinforcement cage horizontally; after being hoisted in a channel, the reinforcement cage is kept in the vertical suspending state, the reinforcement cage penetrates into the trusses repeatedly by a hoisting beam, and then the hoisting beam is placed on the top surface of a guide wall; after steel wire ropes on the second hoisting points are removed, the steel wire ropes are connected with hoisting rings, and the reinforcement cage is lowered gradually; and plane positioning during the lowering process of the reinforcement cage is observed by a level gauge, and the elevation is strictly controlled. The defect of a conventional method for hoisting a reinforcement cage of a diaphragm wall is overcome, the reinforcement cage is kept stable and non-deformed in the process of hoisting, the construction efficiency is improved, and the construction cost is reduced; and the problem that the reinforcement cage of the extra-deep diaphragm wall is inaccurately positioned is solved.