Laser welding was used to weld Ti-3Al-6Mo-2Fe-2Zr（wt.%） β titanium alloy to study the effect of heat treatment on the microstructure and tensile properties of the joint. Since the cooling rate of laser welding can reach 553 K/s,which is much greater than the critical cooling rate for the transformation of β phase to other phases,the microstructure of the weld is composed of a single β phase with columnar crystals. In the near-heat-affected zone,both the primary α-phase and the secondary α-phase transform into β-phase,and theβ-phase grain size increases;in the far-heat-affected zone,the larger primary α-phase remains. After the 780 ℃/1 h/WQ heat treatment,α phase with the thickness of 150 ～350 nm and length of 1 ～3 μm is formed in the fusion zone. Both the strength and elongation-to-failure of the joints increase after the 780℃/1 h/WQ heat treatment. After the 780 ℃/1 h/WQ+500 ℃/6 h/FC heat treatment,α phase with the thickness of 30～40 nm and length of 150～300 nm is formed in the fusion zone. The strength of the joints is further improved with fracture in tensile deformation stage.