Aiming at the poor mechanical properties of coupler of coal mining equipment components in coal mining enterprises of national energy group, the influence of Bi content on microstructure and tensile properties of Al-14Mg2 Si alloy was studied by means of metallography, XRD and mechanical property test. The results show that the alloy element Bi has significant deterioration effect on the primary and eutectic Mg2 Si in the alloy. When the Bi content increased to 0.3%, the morphology of primary Mg2 Si changes from thick and sharp polygon to flat polyhedron, and the average particle size decreased from 43 μm to 24 μm. At the same time, the eutectic Mg2 Si phase changes from labyrinth to short fiber or dot. When Bi content exceeds 0.5%, eutectic Mg2 Si presents metamorphism. Bi can improve the tensile strength and elongation of the alloy. The tensile strength and elongation of the alloy with 0.5%Bi are increased by 34.9% and 90.5%, respectively, compared with that of the unspoiled alloy.