Abstract: Fiber laser bean welding was used to fabricate 8 mm 7A52 alloy plates by butt welding. Microstructures and mechanical properties of the welded joint were investigated. Energy disperse spectroscopy (EDS) was used to measure the burning loss of alloy elements in different regions of the weld. The tensile strength and microhardness of the weld were also measured. The results showed microstructures in the upper area were smaller than that in the lower area, the content of Mg and Zn in the upper part of weld was lower than that in the lower edge. Microhardness in the upper center was higher than that in the lower center, while microhardness at the upper edge was smaller than that at the lower edge. A ductile fracture was observed as the key characteristic for the welded joint, and the tensile strength was 325 MPa, of 65.9% of base metal. The decrease of the tensile strength was caused by the burning loss of Mg, Zn, welding stresses and porosity defects.