Ti6Al4V is an ideal biomedical material with good biocompatibility and excellent mechanical properties, and 3D printing technology is a revolutionary manufacturing technology that can personalized biomedical materials. Therefore, the use of 3D printing technology to prepare Ti6Al4V implants has become one of the hotspots in tissue engineering research in recent years. However, there are a large number of randomly distributed spherical cavities inside Ti6Al4V prepared by 3D printing technology, which hinders the wide use of 3D printed titanium alloy. The formation mechanism of internal cavities of titanium alloy prepared by selective laser melting and electron beam melting deposition is summarized. The effects of high energy beam energy density and scanning strategy on the cavities are analyzed, and the effect of internal cavities on the tensile and fatigue properties of the printed parts is revealed.