The invention discloses a roll forming method of a 2A70 aluminum alloy thin-walled ring forging. In order to roll-form a thin-walled ring forging with high dimensional precision and excellent tissue and performance, the technical scheme comprises the steps of: firstly, sleeving a preheated follower die sleeve and an aluminum alloy pre-rolled blank heated to a deformation temperature in a ring rolling mill, sleeving the follower die sleeve in the pre-rolled blank, and positioning the two workpieces by using a main roll, a core roll, clutching rolls, an upper cone roll and a lower cone roll of the ring rolling mill; and starting the ring rolling mill, making a feeding motion by the core roll towards the direction of the main roll along the radial direction and rolling the pre-rolled blank at a rolling force of 100-2500KN under the support of the follower die sleeve by the core roll together with the main roll to ensure that the pre-rolled blank expands radially at a speed of 4-11mm/s, wherein the wall thickness is gradually reduced, and the pre-rolled blank is rolled into the thin-walled ring forging when the deformation reaches 35-55 percent. The minimum value of the wall thickness of the aluminum alloy thin-walled ring forging roll-formed by adopting the method is 25mm, the maximum value of the height-thickness ratio is 25mm, and the ring forging is mainly used for gyrorotor parts, such as a cylindrical shell and the like used in the fields, such as aerospace and the like.