A system and method for adjustably positioning elevator guide rail. The system includes: an adjustment device arranged on a moving platform and having a clamping portion and a powering portion, the clamping portion being arranged to be capable of clamping an elevator guide rail to be installed through a power output from the powering portion and moving in a first, a second and/or a third directions, and the moving platform being capable of moving up and down in the first direction; a detection device arranged to detect current movement characteristics of the clamping portion when the elevator guide rail is not clamped or has been clamped by the clamping portion; and a control device connected to the detection device and the adjustment device, and arranged to adjust the position of the clamping portion in place by controlling the powering portion according to the movement characteristics.