Aluminum-lithium alloys are considered to be one of the most ideal light-weight materials for aerospace applications. 2198-T851 with thickness of 1.76 mm is welded with filler wire ER4047 by using a high power fiber laser. The effects of the laser power, welding speed and wire feeding velocity on solidification cracking susceptibility and microstructures are investigated, as well as the joint microstructure and mechanical properties under the optimal welding process. The results indicate that a joint with good surface appearance and no hot crack is obtained with the optimal welding parameters of 4 kW laser power, 4 m/min welding speed and 4 m/min wire feeding velocity. The average tensile strength of joints is 342 MPa, and reaches 65.4% of the tensile strength of base metal. The bond is the weakness region of the joint.