Abstract: Based on the phenomenon that a large number of spots appear in the type area on the surface of the gold-plated kovar alloy cavity, combined with the method of electron microscopy, this paper analyzed the structure and composition of the spot area and spots formation mechanism are discussed according to the analysis result. Results show that the spots area is uneven, poor gold layer smoothness is poor and surface area is increased. Water and Cl^- is not only easy to attach to here, and can reach the kovar alloy layer through pore to react to form chloride and oxides, thus forming spots.