藉著檢驗《晉書》（西元六四四年完成）對羌人後秦君主姚興於三九九年稱天王記載的矛盾，並參照四○○年左右佛教在中國所流行的教義與神話，佛教文獻對姚興的記載，以及佛教文化圈內的君主觀，本文指出姚興稱天王乃是受佛教帝釋的啟發，而非來自中國古典《春秋》的天王說。他的統治行為也與佛教的帝釋觀吻合。然而，佛教的天王觀和漢朝以來外儒內法的統治治術背離，使得後秦政權在他死後迅速瓦解。本文為北朝胡人君主使用天王號提出另一個新的解釋。

　　　　　By critically examining historical accounts of a powerful proto-Tibetan king, Yao Xing, who replaced his regal title huangdi (emperor) with tienwang in 399 CE, in an official history, Book of the Jin (completed in 644), the article determines that tienwang actually refers to ?akra/Indra, the ruler of Trayastrim%?? Heaven, often called as devar?ja(king of gods), representing the Buddhist ideal king, rather than the Confucian concept of tienwang (heavenly king) as suggested by other scholars. The article argues for this explanation with materials from various sources: the Buddhist conception of ?akra/Indra in the scriptures and sculptures that were then circulated in China, Chinese Buddhist records on Yao Xing, and the Buddhist usage of devar?ja in the regions other than China. For Yao Xing’s regime was short-lived, the article reaches the conclusion that Buddhism’s political operation in the name of devar?ja was essentially incongruous, and therefore unworkable, with the existing Chinese statecraft.