Though investigating and comparing the microstructure and stress corrosion cracking(SCC)behaviors at different locations of large-size Z-shaped sections of 2224 aluminum alloy in T3511 state,the effects of grain morphology on the SCC resistance and cracking modes were discussed.The results show that the specimens with fibre-like grains have lower stress corrosion sensitivity and are fractured in 52 days at stress of 250 MPa,while the specimens with nearly equiaxed grains are fractured in only 42 days.The nearly equiaxed grains have larger grain size and large-angle grain boundaries with higher interfacial energy,along which the stress corrosion crack is easy to propagate due to the lower grain boundary strength.The cracking mode of the specimens at different positions is all intergranular cracking,and the conductivity value in different positions of the Z-shaped section remains stable.