向來討論《集韻》俗字的議題時，往往只關注到書中注曰「俗作某非是」的字例，而忽略了有一批隱身在異體字列的前代俗字，如此一來將無法正確認識《集韻》處理俗字的觀點與作法。本文旨在觀察《集韻》平聲字中所列的相關俗字例，共計79個正俗字組，這些俗字有的被《集韻》視為異體字而與正字並列；有的則被指為「非是」，透過這些字例的觀察，實有助於了解《集韻》辨正俗字的情形。從本文的研究可知《集韻》辨正俗字的原則有三：重視表音的充分性、表意性及書寫便利性的調和及俗字的構形不宜過度破壞正字的形構。其能重視正俗字關係的隨時變異性，對於能夠符合上述三個原則的俗字，給予翻轉為異體字的空間，得與正字並列，其俗字觀是積極且進步的。嘗試整理出存在其間的觀念及原則，可以做為後人整理異體字的參考；並且釐清《集韻》的俗字觀，也將有利於認識歷代字書俗字觀念的演變與發展。

This discussion of Su Words(俗字) in Jiyun(集韻) focuse on words which are often incorrectly marked. Most people ignore those Su Words of the previous generation which are positioned with the variant Chinese character(異體字). As a result they cannot properly understand the viewpoint and approach of treating Su words in Jiyun. I discusse two kinds of Su words in terms of level-tone words in Jiyun. One is Su Words of the previous generation which are positioned with the variant Chinese character(異體字), and the other is incorrectly marked. By exploring these cases, we can understand the viewpoint and principles of managing Su Words in Jiyun. There are two implications for the research. First, it offers people a reference for arranging the variant Chinese character. Second, it provides people with the benefit of constructing the history of evolutionary relationships among the diachronic notions of Su Words.