This paper is to analyze issues on subjects of state immunity. Part Ⅰ provides background on the doctrine of State immunity, with emphasis on the importance of matters of subjects of state immunity. While Part Ⅱ reviews current judicial opinions, legislation, treaties, and relevant work of the nations and learned bodies including International Law Association and UN International Law Commission on subjects of State immunity, Part Ⅲ studies to what extent the subjects of State immunity cover under international law. Recent important cases relating to the Republic of China are also introduced in Part Ⅱ, and development on issues of head of state and state enterprise are surveyed in Part Ⅲ. In Part Ⅳ, general conclusions and recommendation on subjects of State immunity derived from the developments in Part Ⅱ to Part Ⅲ are present.