The experiment of electroless tin plating on BAg45 CuZn brazing filler was investigated. The effect of plating bath temperature, pH value, plating time on depositing rate and tin content of AgCuZnSn brazing filler were analyzed. The optimal plating conditions were obtained. The surface morphology of tin coating and the wettability of AgCuZnSn brazing filler were characterized. The results indicate that the deposition rate and tin content of AgCuZnSn brazing filler initially increase and then decrease with the increase of bath temperature and pH value. With increasing of the plating time, the plating rate of tin coating also increase firstly and then decrease sharply, but the tin content of AgCuZnSn brazing filler increase gradually. Under the optimized conditions, the tin coating on BAg45CuZn brazing filler is composed of smooth and uniform,then the depositing rate of tin coating is as much as 13. 6 μm / h, tin content of 2. 45% in AgCuZnSn brazing filler. The wettability of the AgCuZnSn brazing filler has greatly improved than the BAg45CuZn brazing filler matrix under the optimal conditions, it possess good spreadability.