As one of the traditional forms of literary criticism since the Han and Wei dynasties, letters on literature played an important role in the establishment of Chinese literary criticism framework. Based on the writers' identities and attitudes, these letters can be grouped into "the presenting type", "the replying type" and "the dialogue type". The theoretical nature of the epistolary style and the contextual constraints resulted from its reciprocal relationship, promoted in-depth scholarly dialogue and avoided the possibility of forcible reinterpretation of the text by later generations. Primary contents in the literary correspondences shifted from summaries of writing experience, reviews of literary history and commentaries on the current state of the literary world, to analyses of literary principles and concepts, and also shifted from self-referential monologues about literature to debates over different characteristics of particular literary genre, and the shifts gradually turned into a practice of literary criticism based on literary community. This intra-community critical consciousness originated from the "Ancient Essay Movement" in the mid-Tang dynasty and reached its peak during the debates over literary schools in the Ming dynasty. Specifically, "Letter to a Friend on Literature" had generalized the object, and this can be better understood when put into the perspective of the internally driven history of literary criticism.