In order to solve the fracture defects in incremental forming， the Oyane criterion was introduced into numerical simulation， and the forming limit of sheet metal in incremental forming was effectively predicted. Firstly， based on DC56D+Z plate and its material constants of the Oyane criterion， the critical value of fracture integral （I=4） was determined by experiment and numerical simulation. Afterwards， by using response surface methodology， a nonlinear model between the process parameters （forming angel α， interlayer spacing Δz and diameter of tool head d） and I was established， and the effectiveness of the model was verified by a parametric analysis. It is found that the value of I can be effectively predicted by the numerical model. The value of I increases with the increase of α， Δz and d. The influence of α， Δz and d on I value gradually decreases in sequence. In addition， the relative large interaction effects of α&Δz and α&d are found.