The 7020 aluminum alloy joints welded by laser-metal inert-gas arc (MIG) hybrid welding are obtained. The microstructure, mechanical properties, fatigue performance and fracture mechanism of these hybrid welded joints are investigated by the techniques of electron backscatter diffraction and high resolution synchrotron radiation X-ray micro-tomography. The results show that, under the influence of thermal circulation in welding, the grain morphology, size and chemical constituent in different zones of butt-welded joints after cooling show obvious changes. The static tensile strength, yield strength and welding coefficient of hybrid welded joints are 265.34 MPa, 218.85 MPa and 0.74, respectively. When the fatigue life is 2×106 cycles and the survival is 50%, the fatigue strength of hybrid welded joints is 96.13 MPa, and is about 63.14% of that of the base metal, which shows that the welding process significantly deteriorates the performance against fatigue. It is found that the fatigue cracks initiate from a notch with 103 μm depth at the surface in the fusion zone, and show a typical I mode quarter elliptical crack profile. The pores have little effect on the crack growth rate in the stable extension stage.