Abstract: The fracture failure of Ti-6Al-4V base in laser selective melting process was analyzed by means of fracture macroscopic inspection, fracture scanning electron microscope and energy spectrum analysis, chemical composition analysis, metallographic , metallographic analysis and CT detection.The results shou that there are a largr number of unfused defects in the U-shaped groove of Ti-6Al-4V base formed by SLM, which leads to the decrease of the bearing capacity of the part, and the overload fracture occurs under the action of instantaneous impact load in the test.Suggestions are put forward: 1、Strengthen online quality monitoring in the printing process, identify and analyze possible risk sources, and strengthen the quality of process detection and control;2、in view of the problems not detected by X-ray and flu orescence detection on the original process route, it is recommended to add industrial CT detection process after machine addition on the original process route.