隨著敦煌文獻在二十世紀初的發現，現代學術意義下的禪史研究隨之展開，其中一項最重大的發現，即是跳脫出深植於傳統燈史裡的南宗本位，充分認知到南宗的正統法脈地位絕不似如燈史所言那樣，由五祖弘忍（602-675）透過傳法授衣所決定，反而是歷經好幾世代的相續經營，最終才從眾禪宗支系中脫穎而出。然而，儘管學人可以確定南宗禪在九世紀末幾已壟斷了禪宗傳承，但對其究竟是在哪個具體時點、通過什麼樣的途徑取得傳承上的優勢，迄今仍存在莫衷一是的看法。本文以為，現有成說雖然各有洞見，然在論證時多缺乏足讓讀者比較、判斷諸系盛衰的有效材料，致使有關論斷常蒙上一層想當然耳的色彩，因此擬回歸最為直觀的辦法，即設法蒐羅自禪門正統之爭展開的八世紀初，至九世紀末的主要禪系人員名單，復尋時序整理各系在不同時間段中的規模與分布狀況，以期建立起一個基本的諸系消長模型，最後再以此作為指引，設法從文獻中發掘能夠印證其興衰曲線的材料，嘗試提出更具說服力的假說。本文將主張，南宗禪的最終得勢，很可能是由會昌毀佛這一政治事件意外促成，換言之，此走向當非勢所必然，而更像是因緣合和的偶然結果。

With the discovery of Dunhuang manuscripts in the early 20th century, modern academic research on the history of Chan Buddhism began to unfold. One of the most significant discoveries was the departure from the entrenched position of the Southern lineage within traditional Chan histories. It was fully recognized that the orthodoxy of the Southern lineage was not established as claimed in the traditional records, which asserted it was determined by the Fifth Patriarch Hongren (602-675) through Dharma transmission and robe bestowal. Instead, it emerged as the result of several generations of continuous operation, ultimately standing out from among the various lineages of Chan Buddhism. However, despite scholars confirming that the Southern lineage had monopolized Chan transmission by the late 9th century, there remains disagreement on the specific time and the means through which it gained its advantageous position in transmission. This paper argues that although existing theories have their insights, they often lack sufficient material for readers to compare and judge the rise and fall of various lineages effectively. Therefore, it proposes to return to the most intuitive method by collecting the names of key Chan figures from the beginning of the 8th century, when the debate over the orthodox lineage of Chan began, to the late 9th century. Then, it will organize the chronological sequence to examine the scale and distribution of each lineage at different time periods, aiming to establish a basic model of the growth and decline of various lineages. Finally, using this as a guide, it will attempt to unearth materials from the literature that can confirm the rising and falling curve, aiming to propose more convincing hypotheses. This paper will argue that the ultimate rise of Southern Chan was likely unexpectedly catalyzed by the political event of the Huichang persecution of Buddhism. In other words, this trajectory was not necessarily inevitable but rather the accidental result of various circumstances coming together.