We propose a method which uses interference-free tool paths to predict and compensate for deformation error during the spiral milling of blades. Firstly, a finite element simulation of the blisk blade milling process was conducted using an interference-free spiral milling NC machining tool path based on the curvature attribute of the blade twisted surface, observing the variation in blade milling error under different processing parameters and yielding a surface quality variation law. Next, the model was corrected by combining this error prediction data with precision design requirements, and a blade deformation error compensation scheme was suggested. Finally, an interference-free processing program containing the error compensation information was applied to carry out another blade milling simulation and a blisk milling experiment. The results showed that both the blade deformation error and the surface quality satisfied design requirements, while the accuracy of the simulation was verified.