Abstract: TC4 titanium alloy was prepared by selecting laser melting technology (SLM), the effect of laser scanning speed on the internal hole, microstructure and mechanical properties was studied by X-ray microscope (XRM) technology, X-ray diffractometer (XRD), scanning electron microscope (SEM)and electron backscatter diffraction (EBSD).The results show that the holes in TC4 titanium alloy formed by SLM are evenly distributed, and the hole morphology is irregular, and it is mainly small-sized less than 80 μm. With the scanning speed increasing, the porosity and the average size of holes increase.The microstructure is mainly composed of acicular α' martensite and a small amount of β phase. With the scanning speed increasing, the average width of primary martensite phase decreases, and the tensile strength and yield strength decrease.