Abstract: The AgCuZnSn alloy is Cd-free and has high strength, makes it has a board application prospect in green manufacture, while the decrease in forming property induced which element limits its application. To overcome that weak point, a method to in-situ synthesis high strength Ag brazing alloy by using AgCuZn/ZnCuAgSn/AgCuZn composite sheet during the brazing process is proposed in the paper. The outer layer of the composite sheet is AgCuZn alloy, and the inner is ZnCuAgSn alloy. The melting points of the two alloys are close and melting point of the inner alloy is lower than the synthesized alloy, and the process ability of the composite sheet is better than the AgCuZnSn alloy with the same composition. Brazing of stainless steel using the composite brazing sheet was studied. It was found that the two alloys melt at the same time, and fused comprehensively after holding for a short time, forming high strength brazing seam. The strength of the obtained brazed joint is much higher than the joints brazed using common AgCuZn alloy.