The application of multi-point dies in the aluminum alloy integral panel forming is a novel forming method. However, how to predict and avoid the instability and fracture of the stiffeners has become a difficult problem in practical application. In this paper, the criterions for instability and fracture of the stiffeners in multi-point forming process were proposed. And the finite element simulation and multi-point bending test were carried out to make a comparison. The results show that the criterions proposed can predict the positions and moments when the instability or fracture occurs. Moreover, the changing of fracture and instability with different bending radius in step-by-step multi-point forming was investigated, and the forming limits of the stiffeners were also found out. The instability and fracture of integral panels with varying path forming were simulated, and the optimal loading path is selected.