Laser welding high strength steel 907A sandwich structure by IPG YLS-5000 laser welding system in this experiment. Tensile properties, microstructure, fracture morphology and microhardness of T-joints are measured by universal testing machine, microhardness tester, super depth of field three-dimensional digital microscope and scanning electron microscope. The results show that, the microhardnesses of welding seams and heat affected zone are higher than that of base metal. The microhardness of weld seam is between 330 HV0.2 and 360 HV0.2. Microstructures of weld seams are lathy martensites, and microstructures of heat affected zone mostly are martensites, residual austenite and a small amount of carbides. T-joint fracture is a composite fracture, which both have ductile fracture and cleavage fracture. In the case that welding speed and coke are certain, weld width and depth increase with higher laser power. Mechanical performance of T-joint mainly depends on the weld width. Under the conditions of this test process, it needs 3 times single laser welding, to ensure that the web and panel joint strength is bigger than the strength of the base metal.