Abstract: Taking domestic 1561 aluminum alloy 40 mm thick plates as research object, the mechanical properties and microstructure of different batches of 40 mm thick 1561 plates were investigated by plate tension specimen, round bar tension specimen, cloth hardness test and scanning electron microscope.The results show that when there is an obvious precipitation zone near the core of the plate, the plasticity and strength of the material decrease obviously, and the crack delamination appears on the tensile fracture.