Cao Zhi wrote Preface to Painting Praise, which is the first painting monograph handed down from generation to generation in the history of China's painting theory. It can be compared with Preface to Mao Poetry in Han Dynasty. Preface to Mao's Poems is the first article devoted to poetry in the history of China, which discusses the ethical education function of poetry. The preface to painting praise advocates the "educational" role of painting. This is of course Confucianism. However, it is very important for Cao Zhi to clarify the social value and significance of painting art and affirm the status of painting art.

Cao Zhi clearly pointed out that painting can "play a warning role". Moreover, this kind of "warning" is not carried out with graphics, but is caused by the emotional voice of the viewer through the artistic image of painting. He talked about the emotional reactions caused by painting, such as "looking up", "lamenting", "gnashing your teeth", "forgetting to eat", "resisting your head", "sighing" and staring at others. This is the first time in China's painting history that different portraits have caused different rich and varied emotional reactions and come into contact with the characteristics of painting art. It is consistent with the first sentence of Cao Pi in Dian Lun Wen that the article should have the temperament of the author. Theoretically speaking, both of them can be said to be pioneers of the era of literary consciousness.