Due to the perfect processing property and sufficient mechanical performance, Ag based filler metal is one of the main jointing materials for brazing. The effect of rare earth Pr on the microstructure and properties of BAg30 filler metal was investigated. The results show that rare earth Pr can increase the melting temperature with ~3℃, improve the wetting spreading area of filler metal on the surface of steel substrate and obviously increase the shear strength of brazed joint, but excessive rare earth Pr would decrease the wettability and shear strength. Based on the content optimization analyze of rare earth Pr, it is found that the optimal addition amount of rare earth Pr is about 0.12%. With the observation of SEM pictures, it is indicated that the addition of rare earth Pr (≤0.12%) can refine the microstructure of filler metal, when the content of Pr is more than 0.12%, the microstructure will be coarsening obviously. The elements mapping demonstrates the uniform distribution of elements and the precipitation of PrCu₆ phase.