To obtain the mechanism of wrinkling behavior of hydroformed torsion beam, numerical simulation and experiments are carried out to analyze the effect of supporting pressure and axle feed on plastic wrinkling behavior during hydroforming process. Stress state and stress locus are gotten by numerical simulation, and they are used to analyze the reason of wrinkling behavior. The results show that the absolute value of axial compressive stress can be reduced by increasing the supporting pressure, and the wrinkling tendency declines. The absolute value of axial compressive stress can be raised by increasing the axle feed, and the wrinkling tendency increases. The wrinkles can appear while the supporting pressure reaches a critical value. To avoid wrinkling, the reasonable load path is that the supporting pressure is 30 MPa and the axle feed is 15 mm for a low carbon steel tube with an outer diameter of 89 mm and a wall thickness of 2.5 mm. 