崑劇日趨細膩的腳色分化，是表演藝術發展的標誌之一，清乾隆時期李斗《揚州畫舫錄》（1795）記載的「江湖十二腳色」，可謂總結分化成熟的崑劇腳色。然而，自乾隆年間至今，腳色仍在變化，本文從舞台演出本、身段譜、談藝錄、前人研究等，析論小生行、末行腳色發展的歷程、探討可能的原因，並與崑劇演出史呼應。小生行、末行是飾演正面男性人物的主要行當，然而從乾隆年間至今，發展趨勢大為不同：小生行分化出五個家門，表演風格從「脂粉氣」轉為「書卷氣」，且取代末行，成為最常擔綱舞台上正面男性人物的行當。末行卻是從三個家門分立，到逐漸兼演，趨於合併，至今總稱老生行，實際配置腳色時，有從「腳色制」往「角兒制」傾斜之趨勢。

The categorization of characters (lines of business) (腳色) in Chinese Kunqu Opera (崑劇) helps the audience to differentiate characters. In each line of business, characters are further differentiated by attributes such as personality, social status, and their function in the script. In some instances, character lines expand, while in others, characters of less significance gradually merge into another line of business.Doe Li (李斗) , a writer in the Qing Dynasty, documented Kunqu lines of business in ”Profile of Yang-Zhou Life” (Yang-Zhou-Hua-Fang- Lu,1795) (揚州畫舫錄). His categorization has been commonly viewed as the authoritative listing of Kunqu characters; however, it appears that the integration and division of lines of business corresponds with the history of Kunqu Opera and continues to change today.This article focuses on the evolution of two character categories, Mo (末行) and Xiao Sheng (小生行), from the publication of Profile of Yang-Zhou Life to the present day. Mo initially included three types of roles: mature males with dark beards (老生) , seniors with white beards (外), and male extras or ensemble (末). The more significant roles in the Mo category have been merged into the Lau Sheng (老生) category (elderly, bearded males), while the less significant ones have become roles that facilitate scene changes or transitions. In contrast, the Xiao Sheng category (young, beardless males) has expanded significantly into five sub-categories, each with a distinct performing style. This article traces the integration and division of these two lines of business and discusses the causes behind their evolution.