周德清（1277-1365）《中原音韻》（1324），包括「韻譜」和〈正語作詞起例〉兩部分。〈正語作詞起例〉共二十七條，最後一條〈作詞十法〉是北曲創作論的經典論述，在中國曲學史上具有開創意義。〈作詞十法〉依序是：（一）知韻（二）造語（三）用事（四）用字（五）入聲作平聲（六）陰陽（七）務頭（八）對耦（九）末句（十）定格。除了「用事」，其餘九法皆與曲牌格律有關。第九法「末句」羅列平仄律；第十法「定格」四十首有評點，若將曲文標示平仄律，可謂曲譜之雛型，為明代《太和正音譜》之先驅。周德清對曲牌舉例的論點雖係吉光片羽，整合歸納之後，實已奠定北曲格律之間架與規模，具有篳路藍縷之功，目前尚無人對此議題有宏觀和微觀的探究。歸納周德清建構曲牌格律之要素有：「句數律、字數律、襯字律、聲調平仄律、末句律、收煞律、協韻律、務頭律、對偶律」。本文以北曲格律之各項要素為經，以〈作詞十法〉各項法則及其「末句」平仄律、「定格」四十首評點為緯，兼以現存元曲為輔證，全面觀照周德清對北曲格律之建構，並評議其得失與影響。

Zhou De-Qing’s (1277-1365) Zhongyuan Yinyun (1324) includes “Rhyming Groups” (Yunpu hereafter) and “Zhengyu Zuo Ci Qili” (Qili hereafter). Among the twenty-seven guidelines of Qili, the last one “Zuoci Shi Fa” ‘ten rules of lyric composition’ introduces classical discourses of creation theory in the beiqu ‘Northern traditional opera.’ The tenth rule is considered a meaningful initiative in the history of Chinese Traditional Opera. The ten rules refer to zhiyun ‘knowing rhymes,’ zaoyu ‘creating language,’ yongshi ‘the use of events,’ yongzi ‘the use of words,’ rusheng zuo pingsheng ‘using entering tone as level tone,’ yin and yang, wutou ‘the most euphonic sentence/word/tune,’ duiou ‘antithesis,’ moju ‘the last sentence,’ and dingge ‘freeze.’ All rules are related to metrical patterns of qupai ‘names of qu’s tunes’ except yongshi. Moju lists tonal patterns while dingge adds comments on forty pieces and, based on the tonal patterns marked on qu, thus becomes the prototype of qupu, the predecessor of Taihe Zhengyinpu in the Ming. Zhou’s theories on the examples of qupai are fragmental, but highly valued. After being summarized, his work has established the structures and metrical patterns of Beiqu, and thus should be given credit for his macroscopic and microcosmic points of views on the investigations into qupai. The key elements of Zhou De-Qing’s construction of metrical patterns of qupai are “jushu ‘metrical patterns of numbers of sentences,’ zishu ‘numbers of regular words,’chenzi ‘numbers of additional words,’ shengdiao pingzhe ‘level and oblique tones,’ the last sentences, shousha ‘end and pause,’ xieyun ‘harmonization,’ the most euphonic sentence/word/tune, and antithesis.” Based on the extant Yuan opera, this article analyzes Zhou De-Qing’s construction of metrical patterns in the Northern traditional opera and comments on the advantages and disadvantages of his work and his influence on later scholars.