Concrete top plate supporting device for narrow space of building structure

The utility model discloses a narrow space concrete top plate supporting device of a building structure, which comprises a plurality of I-shaped steel supporting beams arranged below a pre-cast concrete top plate in a supporting manner, and supporting square steel capable of adjusting the horizontal length is arranged between two I-shaped steel supporting beams. The supporting square steel is of a U-shaped structure which comprises a horizontal straight line section and vertical upward sections at the two ends of the horizontal straight line section, the vertical upward sections enable the supporting square steel of the U-shaped structure to be detachably hung and fixed to the two I-shaped steel supporting beams through hanging pieces, and at least two sliding sleeves are arranged on the horizontal straight line section of the supporting square steel. A height-adjustable supporting pillar is fixed on the sliding sleeve; and the supporting pillar supports the concrete top plate pouring template through the sup