The invention discloses an assembly type reinforcement cage lowering frame and a reinforcement cage lowering method. The lowering frame comprises four vertical pillars, four upper cross beams, four lower cross beams, two fixed pulleys, two movable pulleys and two steel wire rope I, wherein connection lines of tops of two adjacent vertical pillars form a square; an upper cross beam is arranged between the tops of any two adjacent vertical pillars; a lower cross beam is arranged between the bottoms of any two adjacent vertical pillars; the two fixed pulleys are located at the bottoms of the two opposite upper cross beams respectively; the two fixed pulleys are detachably connected with the corresponding upper cross beams; a connection line between two fixed pulleys is perpendicular to two vertical pillars which are connected with the two fixed pulleys; a movable pulley is arranged under each fixed pulley; a steel wire rope I is wound on each fixed pulley and the movable pulley corresponding to the fixed pulley. Through the assembly type reinforcement cage lowering frame and the reinforcement cage lowering method, the safe, rapid and economical technical support is provided for extending, lowering and mounting the reinforcement cage, so that the lowering frame has sufficient lifting capability and is capable of ensuring that the reinforcement cage is smoothly lowered in place.