The present disclosure discloses a method for forming a rim of a cast-spun aluminum alloy hub, that is, a special spinning composite machining method for forming a structure that the spokes and the inner wheel flange of the hub are cast and the middle of the rim is spun. The method can prevent the performance, strength and as-cast structure of the inner wheel flange from being destroyed, effectively improve the impact resistance of the cast-spun hub at the inner wheel flange, prevent the inner wheel flange of the cast-spun hub from cracking during radial impact and improve the performance of the spun structure of the rim, is beneficial to thinning the rim and realizes light weight of the rim.