唐朝流行之詩歌，當時稱為「曲子」或「曲子詞」，意味著搭配音樂而吟唱的詞語。隋唐時期歌謠中，以正式資料傳至後世的民間歌謠極少，如今所見到的多數曲子，即是二十世紀初發現於敦煌莫高窟的敦煌曲。敦煌曲之體式以雜言體為主，其中三言句、四言句之出現率相當高，此種形式也使得曲子發揮了引人屬目的種種效果。中國古代詩歌之主流體式自四言體起始，在時代過程中蛻變為五言體、七言體，五言體與七言體逐漸成為中國詩歌歷史中的兩大體式，四言體則隨著時代變遷而減少，《詩經》之後再無以獨立體式而盛行。然而四言句則經常出現於雜言詩歌中，尤其是常出現於敦煌曲中，其出現率僅次於三言句。

筆者從敦煌曲體式之研究得出，若將五言句、七言句視為中國詩歌中的定型節奏，混合於雜言中之三言句、四言句，能夠打破定型節奏而醞釀出更複雜、更具生動節奏感的效果。本文將以敦煌曲體式中高頻率出現之三言句、四言句的此項特色為主題，探討其中表現形式與雜言節奏感之關係。

The popular songs of the Tang Dynasty was called "quzi" or " quzi ci" at that time, and many of them that we can see now are Dunhuang songs which were discovered as part of the Dunhuang documents. The formal feature of Dunhuang songs is the zayan-ti and the high occurrence rate of three and four-syllable phrases. The main form in Chinese classical poetry started with four-syllable composition, and it transited to five-syllable, seven-syllable, five-syllable poetry and seven-syllable poetry became the two major poetry types in Chinese poetry, four-syllable poetry declined as the times changed on the contrary. However, four-syllable phrases are often seen in poetry of zayan-ti, it is especially used in Dunhuang songs, and its high occurrence rate is the second after the three-syllable phrases. This paper assume that if five and seven-syllable is a fixed rhythm in Chinese poetic songs, three and four-syllable mixed in zayan-ti breaks its rhythm and forms a more complex rhythm. This paper recognize the heavy use of three and four-syllable phrases as a formal feature of Dunhuang song, and consider the relationship between its appearance form and the complicated rhythm of zayan-ti.