According to the serious problem in milling cutting , experiment of cut-in impact disrepair has been done. Based on the method of experiment data and mathematical analysis, cumulate function of cut-in impact disrepair was founded with Weibull software and Matlab software. The cut-in style with minimum disrepair was optimized. The results showed that the U style has the longest cutting length, the most impact-resistant times, and the best ability of impact-resistant disrepair. The sequence of impact-resistant disrepair was U style, V style, T style, and S style. The theoretical basis was provided for the application of 3D complex groove milling insert in reason.