Abstract: A filler composition for welding onto a substrate is composed of 82.5˜96.5 wt %, aluminum, 3.0˜10.0 wt % copper, 0.2˜1.5 wt % magnesium, 0.1˜1.5 wt % silver, 0.1˜2.0 wt % scandium, 0˜1.5 wt % zirconium, and 0˜1.0 wt % titanium, and can be welded with a high success rate to a substrate (such as an aluminum-copper alloy substrate) and avoiding a hot cracking phenomenon and a low welding strength, so as to achieve the effects of enhancing the yield rate and lowering the cost of a product.