The invention discloses a large round roof fan hood spinning device, which comprises a base and an upright post fixed on the base, wherein the top end of the upright post is fixed with a cross beam, a primary pressing mechanism is fixed in the center of the cross beam, and a primary pressing upper die is arranged on the primary pressing mechanism; and the base is also fixed with a primary driving machine and a primary rotating shaft which is in transmission connection with the primary driving machine, a primary pressing lower die is arranged on the upper end of the primary rotating shaft, and a spinning mechanism is also arranged on the base and comprises a spinning upright post, an internal rotating cross beam, an internal rotating shaft, an internal rotating ejecting die in rotational connection with the top end of the internal rotating shaft, an external rotating shaft and an external rotating ejecting die in rotational connection with the lower end of the external rotating shaft. When the large round roof fan hood spinning device disclosed by the invention is used, a large stainless steel round roof fan hood can be processed on small hydraulic equipment by primary pressing positioning and performing secondary hood spinning processing through the spinning mechanism under the pressing action of the primary pressing upper and lower dies.