TC4 titanium alloy was fabricated by selective laser melting( SLM). The influence of annealing treatment on the microstructure and mechanical properties were investigated in details. The results show that the microstructure as epitaxial growth columnar with fine acicular martensite phase. After annealing treatment,the microstructure changes from martensite phase to staggered basketweave α + β microstructure. With the increasing of annealing temperature,the content of α phase decreases,the size of α phase and the content of β phase both increases. With the increasing of annealing temperature,the room temperature tensile strength and micro-hardness decrease and the plasticity increases.The better strength/plasticity matching of TC4 titanium alloy formed by SLM can be obtained by the annealing heat treatment of 800 ℃ × 2 h/FC.