Abstract: To study the effect of spot diameter on the shaping of selected laser melting（SLM） Ti-6Al-4V（TC4） alloy, 9groups of 50-210 μm spot diameter samples were used to form the samples, the density, surface roughness, microstructure and properties of the samples before and after annealing were analyzed. It is found that with the increase of spot diameter, the surface roughness of the sample increases, the density decreases obviously, and the strength decreases significantly with the decrease of the density. The density and surface roughness of the sample printed by the 70 μm diameter laser spot are best,which are 97.58% and 12.6 μm, respectively, and the tensile strength reaches 1201.7 MPa. After annealing the sample at 850℃/2 h with furnace cooling, the unstable α’ martensite microstructure of the sample decomposed into a stable（α +β）microstructure, the β phase increases, and the α phase grows. The side surface hardness decreases by 4-7 HRC, the tensile strength decreases by 22.7% at the highest, and the reduction of area increases by 6.9%. The results show that the annealing can obtain better strength and plasticity for SLM printing TC4 titanium alloy with 70 μm spot diameter.