葉燮的著作中，以《原詩》最受人矚目。《原詩》分為內、外兩篇，二篇中又分上、下，葉燮在這四內中，建構出一個完整而有系統的理論體系。所謂「原詩」，顧名思義，即是論詩歌之源，這正是《原詩》全書理論之核心。細觀全書，大致包含有詩歌發展論、創作論及鑑賞論等內容。 葉燮的詩歌發展論，主要論點就是從「正變」出發，他不僅將「正變的」的觀點納入整個詩歌文學發展的歷史去考察，歸納出外在時代風氣的影響，以及內在詩歌本質的因素而產生變化的結果之外，能將詩歌的演變歷程，正變、盛衰、本末、源流之理，作出系統而條貫的分析，對明七子復古理論的針砭，也能一針見血，能破而能立，此其詩歌發展論之所以受到重視的緣撤，也是其價值所在。

Ye-Xie constructs a whole and systematic theory in his writing “Yuan-shi”. It contains the development of poetry and the method to write and appreciate. Ye-Xie’s theory of the poetic development focus on the viewpoint of “cheng-pian”, and he generalizes a conclusion that time custom and the intrinsic essence of poetry have a great influence on the poetry. Besides, Ye-Xie’s criticism that aim directly at “chi-tzu” is also very brilliant. That is why Ye-Xie’s “Yuan-shi” was considered important.