The butt welding of 3 mm thick 7050 aluminum alloy plates by using fiber lasers is conducted. The effect of welding process on weld forming is studied, and microstructures, chemical compositions, mechanical properties and fracture characteristics of joints are also investigated. The results show that well joints can be obtained when laser power of 3 kW, welding speed of 4 m·min -1, and spot diameter of 0.2 mm are chosen. There exist mainly equiaxed grains in the weld center, Al-Cu intermetallic compounds are dispersed in the grain boundaries, there are mainly columnar dendrite grains in the weld edge, and the heat affected zone (HAZ) is relatively narrow. No precipitation is found in the weld and the strengthening phase in the HAZ melts slightly. The microhardness distribution of weld joints is non-uniform, the hardness at the weld is the lowest, and there exists obvious softening in the HAZ. The tensile strength of welded joints is 307 MPa, the joints fracture along the weld after tensile, and there exist small dimples in the fractures, which shows a character of intergranular brittleness fracture.