Abstract: Ti6 Al4 V test specimens were prepared by selective laser melting（ SLM）. Influence of laser process parameter on densification behavior,microstructure and mechanical properties of Ti6 Al4 V alloy specimens was researched. Microstructure and comprehensive mechanical properties of SLM formed samples were analyzed by metallographic microscope and tensile testing machine and other test methods. The result showed that the average density of the sample at different laser scanning speeds increased from 85. 3% to 94. 5% with the laser power increasing from 360 W to 400 W,and the density increased significantly. As the laser energy density increased,the porosity decreased significantly and the acicular martensite α’ phase with better plasticity and strength distributed uniformly. Using the optimum process parameter（ P = 400 W,v = 2 100 mm/s）,the tensile strength and yield strength of the specimens were 1 159 MPa and 1 008 MPa,respectively,which were higher than the forging standard. After annealing at 800 ℃ for 2 h,the elongation and reduction of area increased by 2. 26 tiems and 2. 68 times,respectively,with a large increase. Both α’ and β phases transformed into α + β phase,and grain coarsening weakened the grain boundary inhibition effect of internal slip deformation,which resulted in the material strength decreasing and its plasticity increasing remarkably.