Abstract: Microstructure and its characteristic of ZA soldered joints, distribution of Sn elemont and reaction product of Sn in interface of ZA alloy soldered joints are studied by optical microscope, scanning electron microscope and electron probe microanaly sis, reskectively.The results show that Sn mainly diffuses by volume diffusion and forms a wide diffusion zone.Sn in interface also reacts with some elements in parent metal.New phases such as α-CuSn and Cu₂₀Sn₆ are formed.The diffusion and reaction of Sn will be propitious to the bonding strengths and mechanical properties of soldered joints, which can satisfy the service performance of soldered joints.