Blisk and other complex surfaces parts are the core parts of aircraft engine parts，tool path planningtechnology is the key technology in CNC machining． This paper analyzes the current domestic and foreign researchstatus and the development of the tool path planning for complex surface parts in NC machining． Comparative analysisis mainly carried out for three main tool path plans in complex surface machining，and the key techniques of tool pathplanning has also been analyzed，including: the algorithm theory and application features of track topology，trajectoryparameters，interference avoidance and tool axis control． In addition，the development direction of curve interpolationand tool preferred combination in tool path planning techniques has been analyzed and previewed． These laid thefoundation for subsequent work of complex surface parts high efficiency and high quality CNC machining．