本文由司馬昱生活的五十四年中，來觀察探討自東晉初期元、明之後帝位更迭的背景，並凸顯琅邪、會稽二封王在東晉皇權政治中地位的消長；以及從司馬昱的佈局與作為，分析孝武帝即位的背景。 三十八年遠離政治中心的爭鬥，司馬昱得到另一種的發展，亦即有別於其他司馬氏，走向玄學的發展，雖然在當時司馬昱被譽為第二流的玄學家，但在他提倡下，東晉中期以前會稽地區玄學呈現豐饒的的發展。也由於在會稽的長期經營，結交了一批文人雅士，這些人與司馬昱不但在文學清談中酬酢，也在司馬昱的政治發展中扮演謀士與實際執行者的角色。 從簡文帝司馬昱的研究，不只可以瞭解其一生的發展與重要性，另外更可觀察東晉自元帝以後至孝武即位前東晉帝位繼承之爭的另一面向；另也提供吾人從另一些角度，看待權臣與外戚操弄政權的手腕與結果。

The life of Jian-wen Emperor Si-Ma Yu of East Jin can be divided into several stages in his life. The first stage is from his birth until the death of his mother Imperial Concubine Cheng. His father, Si-Ma Rui, had six sons from four mothers. Because of the status of his mother, Si-Ma Yu was favored by Si-Ma Rui, and received the title of “Lang Ye Wang” at the age of three. However, soon after Si-Ma Rui passed away, his mother, Cheng, passed away in year 326. Si-Ma Yu became a thorn in the flesh to the political struggle, and his title was degraded to “Kuei Chi Wang” for 38 years. For 38 years, Si-Ma Yu was kept away from political struggle and devoted to the development of metaphysics. Under his initiation, the development of metaphysics before the middle of East Jin was prosperous. In terms of politics, he experienced over six Emperors, Ming, Cheng, Kang, Mu, Ai, and Fei. He was nominated twice for the Emperor but lost the political battle. Because he managed to stay out of the battle, his governmental rank kept rising and unharmed. After Fei Emperor ascended the throne, Si-Ma was appointed Lushang Shushi and Fujun General, and began to have political control. He introduced his connections in Kuei Chi and metaphysics to the central government, and those people had significant effect on the war against other countries and internal affairs during the Fei Emperor period, as well as on the power struggle against Huan-wen after Si-Ma Yu became the Emperor. This paper would discuss the alternation of the thrones of East Jin since the early period, the vicissitude of the titles “Lang Ye Wang” and “Kuei Chi Wang” in the political positions, and the political arrangement and movement of Si-Ma Yu, to analyze the background of the enthronement of Hsiao Wu Emperor.