The mechanical properties and microstructure of TC4 titanium alloy prepared by selective laser melting（SLM） after annealing treatment were investigated. The results show that the TC4 sample formed by selective laser melting is mainly composed of acicular α′ phase. With the increase of annealing temperature

α′ is gradually decomposed into α+β phase

and gradually transformed from Widmannstatten structure to basket structure. The elongation is increased gradually with decreases of the yield strength

and the tensile fracture presents ductile fracture. The results show that the alloy present the satisfied mechanical properties with annealing at 800 ℃ for 90 min

with a tensile strength of 902.43 MPa and elongation of 2.38%.