The effect of microstructure on fatigue behavior of 7020 aluminum alloy profile was investigated by optical microscopy, scanning electron microscopy, scanning transmission electron microscopy and electron back scattering diffraction technique. The results show that the fatigue strength of the alloy is 232.9MPa at 107 cycles of loading, under the stress ratio R of 0. The fatigue crack growth rate is about 6.44×10-5mm/cycle at ΔK of 8MPa·m1/2. The coarse high-melting intermetallic compounds with a size of 3 to 12μm in the alloy not only easily become the initiation of fatigue crack, but also accelerate fatigue crack growth. In the unrecrystallized area, the fatigue crack growth of the alloy mainly occurred by a transgranular mechanism. When the adjacent grains are small equiaxed recrystallized grains with high misorientation, fatigue cracks would propagate rapidly along the grain boundaries. The lower the proportion of recrystallization and its corresponding high-angle grain boundaries, the more tortuous of the fatigue crack propagation path. Under these conditions, the fatigue crack of the alloy propagates slowly.