A new tool path generation method based on Z-buffer method is proposed for free-form surface machining by using ball-end cutters. Firstly, to avoid ball-end mill cutting the workpiece, we make the cutter shaft which is perpendicular to machining surface tilt angle θ, then determine the examining area and then judge there is or not a interference occurring between ball-end mill and examining area, if there is, then make a adjustment for cutter shaft. The discretized points within the examining area are efficiently read in and stored directly by the computer hardware; no extra searching and iterative methods are needed. Simulation results show that, comparing with the traditional algorithm, the tool-position calculation time is shorter, and the phenomenon of workpiece squeezed and scratched is less in this algorithm. It meets the basic needs of five axis machining accuracy. Finally we make a practical machining experiment for cutter location generated.