The spinning process of a hollow part with triangular arc section is numerically simulated with the finite element software MSC.MARC,and the corresponding stress-strain distribution is investigated.Then,the forming quality affected by the axial feed rate of the roller and by the thickness-to-diameter ratio of the blank is investigated.Moreover,the causes of such forming defects as wrinkling,thinning and rebounding are analyzed,with the defect positions being also determined.Simulated and experimental results show that the wrinkling,thinning and fracture of the hollow part with triangular arc section mainly occur in the mouth region（i.e.,the blank flange that occurs during the forming process）,the lower region of wall near the fillet and the small arc in the fillet region.