Abstract: The Ti-6Al-4V base formed by Selective Laser Melting（SLM） experienced fracture failure during the experimental process. The fractured base was analyzed by macroscopic fracture inspection, scanning electron microscopy and energy spectrum analysis, chemical composition analysis, metallographic analysis, CT detection and other methods. The results showed that there were a large number of incomplete fusion defects inside the U-shaped groove of the Ti-6Al-4V base formed by SLM, which led to a decrease in the load-bearing capacity of the area. Under the action of instantaneous impact load in the experiment, overload fracture occurred. And put forward suggestions: First, Strengthen online quality monitoring during the printing process, identify and analyze possible risk sources, and enhance process detection and quality control; Second, To address the issue of undetected lack of fusion defects in X-ray and fluorescence testing, it is recommended to add an industrial CT sampling process after the original mechanical processing.