The utility model relates to a round structure with a prestressed sheet metal roof, which comprises a structural frame and sheet metal roof panels. The structural frame comprises an outer ring frame, an inner ring frame, lower string cables, endless cables and panel support rods; the outer ring frame comprises annularly distributed steel columns and an outer ring beam; the inner ring frame is positioned at the center of the outer ring frame and comprises an upper inner ring beam, a lower inner ring beam and inner ring support rods; the inner ring support rods are supported between the upper inner ring beam and the lower inner ring beam; the outer ring beam and the lower inner ring beam are connected by the lower string cables and perpendicular to the lower string cables; the endless cables are arranged between the outer ring beam and the lower inner ring beam at intervals; the panel support rods are arranged on intersection top surfaces of the endless cables and the lower string cables; and the roof panels are paved on an inclined surface formed by the upper inner ring beam, the outer ring beam and the panel support rods. The round structure overcomes the shortcomings of easiness in deformation and damage of an existing tensioned membrane stressed jointly with a linear structure, realizes joint stress of the structural frame and the roof panels, and can be widely applied to the structural form of a large-span steel structure.