Titanium alloy membrane disk is a typical part in aerial engine and it belongs to variable cross-section thin-wall part, which is apt to change its nature and difficult to machine. Serrated chip is prone to create in the machining process. A periodic serrated chip will cause high frequency undulation of the cutting force, and further leads to the cutting tool wear and affect the surface’s integrity. Based on the turning of titanium membrane disk, this paper used metallographic microscope and SEM to observe the morphology and micro shape of the chip, and analyzed the influence of cutting conditions on chip formation and the reason for serrated chip. Finally, a FEM analysis on the chip formation process is completed. Analysis results show that under all the set cutting conditions the serrated chip was formed in the machining process. The shearing slippage and fracture caused by dislocation movement can better explain the formation mechanism of serrated chip. The feed rate has great effect on the chip formation and the forming frequency of serrated chip. The FEM analysis results primly consistent with the experiment results, which can accurately forecast the cutting force, the distribution of temperature and the surface quality.