The invention relates to a construction supporting platform of an elevator well and a construction method thereof. The construction supporting platform comprises a rectangular platform frame formed by enclosing four borders, wherein a steel plate is paved on the frame; a manhole and a movable cover plate are reserved in the middle of the frame; at least two vertical supporting columns vertical tothe platform frame are downwards arranged on one border of the platform frame; another border opposite to the border with the two vertical supporting columns is downwards provided with two oblique supporting columns; a human pedal is welded in the middle of an oblique supporter; the lower ends of the two oblique supporting columns are connected with the lower ends of the two vertical supporting columns to form a right-triangle supporter; and the lower ends of the two vertical supporting columns are provided with right-angled supporting legs. The construction supporting platform and the construction method thereof change the conventional way of a double-pole scaffold in the construction of the elevator well, saves cost compared with the double-pole scaffold, and avoids potential safety hazards caused by paving the double-pole scaffold when the well is ultrahigh; and the construction supporting platform has a simple structure, is convenient to mount, is used repeatedly, and saves work, time, labor and material cost.