Abstract: The effects of the addition of Ti and Sr on the microstructure of ER4043 aluminum alloy welding wire and its tensile strength of butt-welded joints with ER4043 as consumable were investigated. Experimental results show that adding a small amount of Ti can refine α-Al matrix and modify the eutectic silicon, leading to a change in the morphology of eutectic silicon from the large brittle flake or acicular to fine fibrous morphology, thas resulted in the improvement of the mechanical properties of ER4043 aluminum rod and butt-welded joint. When the content of Ti was at 0.08%, the tensile strength of the joint reached 166 MPa which is 5.7% higher than that of unmodified ER4043 aluminum alloy welding wire. With the appropriate addition of Sr the refinement of α-Al was more obvious and the granular eutectic silicon phases evenly distributed. Moreover, when the content of Sr was at 0.02%, the tensile strength of the welded joint reached the maximum value 187 MPa, which enhanced 19.1% compared with the joint welded with unmodified ER4043 aluminum alloy wire. By comparing the data as mentioned above, it can be found that the modification effect of Sr on the ER4043 aluminum alloy is significantly superior to that of Ti.