What is China's earliest poetry criticism?

Zhong Rong, a native of Yingchuan Changshe (now Changge, Henan), was a literary critic during the Qi and Liang Dynasties in the Southern Dynasties. His poetry is the earliest monograph of poetry criticism in the history of China literature, and it is also an outstanding masterpiece of literary criticism after Liu Xie's Wen Xin Diao Long. Zhong Rong wrote this book because of the decline of poetry and the seriousness of formalism at that time, focusing on allusions, sticking to melody and ignoring the content. Poetry is a three-volume book, which specializes in the origin, development and different schools of five-character poetry. The author commented on 122 poets from the Han Dynasty to the Qi and Liang Dynasties, which were divided into three categories: upper, middle and lower, hence the name "poetry". Each product is arranged in chronological order, and each poet has made a brief introduction and put forward many incisive opinions on the characteristics and order of his works. This book is a critical monograph with profound attainments in poetic theory, which has great influence on later generations.