Abstract: The effects of Ag on the microstructure of Zn- Al filler metals were studied,and it was found that Ag addition could refine the microstructure of Zn-Al filler metals.The fracture mechanism of brazed joint was analyzed based on the microstructure, mechanical properties and fractograph.The results show that brittle blocky CuAl₂ phases could not synchronously and coordinately deform with the surrounding phases under external forces.The stress concentration occurred easily on the boundary of CuAl₂ phases and resulted in cracking which led to joint fracture.By adding Ag,the CuAl₂ phase became finer and the joint strength increased.When Ag content was 3.3wt.% in the filler metal,the joint strength reached the highest.Meanwhile, the dimples were large and deep in the fractured surface.