The invention discloses a tin alloy for copper alloy hot galvanizing. The tin alloy consists of the following elements in mass fraction: 1.5-11.0% of Zn, 0.2-1.0% of Mg, 0.2-3.5% of Bi, 0.1-0.5% of Cu, 0.05-0.2% of RE and the balance of Sn and inevitable impurity elements. The tin alloy has the advantages that components of the alloy are relatively simple, the cost is low, IMC thickness of a hot coating is small, and is small in increasing trend, cavities and crystal whiskers are liable to generate in use and the like, and can be used for hot galvanizing and deep processing of copper and the copper alloy. A copper plate belt product subjected to hot galvanizing treatment through the alloy disclosed by the invention is mainly used for manufacturing various electronic connectors, electronicsplicing parts and the like in the fields such as integrated circuits, electronic electrical apparatuses, intelligent equipment and the automobile industry.