The bottom-locking joint laser welding experiments between titanium alloy TA15 plate with a thickness of 1.8 mm and ZTA15 as-cast conditions with a thickness of (1.8+1.8) mm were carried out by disk laser. The internal quality and microstructure of the welded joints were observed by using X-ray diffraction and metallurgical microscopy, respectively. Mechanical properties of laser welding of bottom-locking joint was also evaluated. The tensile fracture of the bottom-locking joint was analyzed by scanning electron microscope. The results show that good internal quality and forming with the appearance of sliver and white weld can be obtained when welded with reasonable welding parameters. The excellent mechanical properties of the bottom-locking joint can be also obtained in the meantime. The microstructures in the center of weld seam and heat affected zone are composed of slender acicular martensite α′+ α-phase+β-phase. The tensile fracture site of bottom-locking joint mainly appears in the weld seam area. The titanium alloy laser welded joints show a mixture of ductile and brittle fracture after tensile test.