The Case of Rosa v. Huo-Yan Wu (2002/08/16-2003/11/13, about the custody of Iruan Ergui Wu) has been settled since Iruan retuned his grandmother’s home in Brazil. But it’s still worthy to study the issues about child welfare system in Taiwan that have been discovered from this case. In order to approach this aim, the author gathered all the judicatory judgments about the custody of Iruan first, and then made a table to illustrate the story and the juridical process. After the procedure above, this article tried to make a conversation with the court though the explanation of the custody institution in Taiwan. By conforming the whole frame f the custody institution in Taiwan, the author explained the key points of law argument in the Case of Rosa v. Huo-Yan Wu and commented the judicatory judgments, especially on the decision about the best interest of Iruan. Generally speaking, the judicatory judgment in correspond to due process of law and supported by some important science opinions, which are worthy to adopt in the similar cases in the future.