Thick-walled cylindrical parts with external grooves are common components in the automobile and aviation fields. Such components can be produced by pressing the outer surface of a spinning thick-walled aluminum alloy tube by the dieless radial spinning process. The forming characteristics in the spinning process and the effects of various process parameters on forming were studied by using orthogonal tests and finite element simulations. During the forming process, bulge and thickness reductions occur because of material flow. The results of an investigation of process parameter effects show that the stress yield ratio (ξ) had no significant effect on forming. However, the feed thickness ratio (η) and initial wall thickness of the tube (t0) crucially affected the forming quality (e.g., the heights of bulges and thickness reduction in the groove area). Thick-walled tubes presented different phenomena compared to the thin-walled.