漢語小稱詞長久以來已為學術界熱烈討論。然而，大部分研究的弱點在於語料與理論脫離、共時與歷時二分。有鑑於此，本研究以優選理論中的部分排序制約為架構，分析粵北土話小稱詞的歷時演變。我們首先回顧粵北土話小稱詞的形成方式，及其在優選理論架構下的分析。緊接著，我們利用部分排序制約來分析粵北土話小稱詞，並特別注意二個要點的詮釋：「非決定性的排序」及「去口腔阻塞化」。研究顯示，部分排序制約架構的應用，不僅可以解釋語言演變的動機，更可以解釋語言變化的選擇性。

Previous studies of Chinese diminutives usually fail to connect language
descriptions to linguistic theories, and fall into a dichotomy between synchrony and diachrony. In view of these, this study, based on the diminutives in Yuebei Tuhua (YBTH), targets for the gradualness of diachronic change in terms of partially ordered constraints (POC) under the framework of optimality theory (OT). It first reviews how YBTH diminutives are formed, and how they are analyzed under the OT framework, based on Cheng (2006) and Chung and Cheng (2007). Then, POC is applied to these YBTH diminutives, with special attention given to two issues, noncrucial ranking and debuccalization. This study shows that POC works well to capture not only the motivations in diachronic change, but also the optionality in language variation.