In recent years, aero engine parts with complex shapes are increasing due to demand on improved performance and weight reduction. In one example, some of those parts have groove which are deep, narrow and complex surface. They are processed by Simultaneous 5-axis machining with small ball end-mill. However, its complex groove shape cause greatly move of tool posture, thereby it cause greatly and discontinuous move of rotational and tilting axis of machine tool. As a result, actual feed speed cannot follow the commanded feed speed, so low process efficiency is problem. It can be considered simultaneous 4-axis machining which with fixed tilting axis as countermeasure. However it is difficult to generating tool path of simultaneous 4-axis machining by commercial Computer Aided Manufacturing (CAM) software for these deep groove shapes because of its tool collision avoidance algorithm. In this study, we developed method of generating tool path that can be machining simultaneous 4-axis machining while avoiding collision of workpiece and tool as an aim of increasing process efficiency. Furthermore, In order to effect of further improve the feed speed, we studied about posture planning way with possible to continuous moving of rotational axis, and we conducted verification test of increasing of feed speed with proposed method.