Abstract: Pb-Mg-Al alloys with boron were prepared by vacuum smelting method, and the effects of boron content on microstructure and mechanical properties of the alloys were studied by scanning electron microscopy, X-ray diffraction, energy spectrum analysis and mechanical property testing. The results show that the black particle phase of AlB2 appeared in the microstructure of the alloy after adding boron, which followed the Mg-Mg17Al12 eutectic structure to grow. The distribution of the AlB2 phase was homogenized and the Mg-Mg17Al12 eutectic phase increased with the increase of boron content. The mechanical properties of the alloy with 1wt% boron were the best, and the tensile strength, hardness and elongation were 105 MPa, 160 MPa and 6.87%, respectively, and its room temperature tensile fracture was mainly the mixture feature of tough fracture and quasi-cleavage fracture.