Increasing the layer thickness can significantly improve the preparation efficiency of selecting laser melting formed Ti-6Al-4V. However, it leads to lower forming quality in comparison to the alloy with low layer thickness. Annealing heat treatment can improve the ductility of titanium alloy prepared by selective laser melting, but the effect of annealing heat treatment on the sample with high layer thickness is not clear. In this research, the Ti-6Al-4V with high layer thickness was fabricated by selective laser melting. The 700 and 950 ℃ were set as annealing heat treatment temperatures, and the effects of heat treatment on the microstructure and properties of Ti-6Al-4V were investigated. The results reveal that the preparation of samples can achieve good forming quality when the scanning speed ranges from 600 mm/s to 800 mm/s. After annealing at 700 and 950 ℃, the microstructure of the samples transforms from acicular martensite to lath martensite. The β phase can be observed after heat treatment at 950 ℃. The changes in compression performance are influenced by the microstructure. The ultimate compressive strength of the prepared sample with a scanning speed of 600 mm/s is 1593 MPa, and the maximum fracture strain is 15.1%. After annealing heat treatment, the ultimate compressive strength decreases to 1359 MPa and the maximum fracture strain increases to 22.2%. The fracture mode changes from brittle fracture to ductile-brittle fracture.