The purpose of this study is to clarify the process and structure of forming critical literacy in educational practices. I focus on Paulo Freire's theory of literacy and Henry Giroux's radical reconsideration about Freire's theory of literacy. Freire regards literacy as a form of cultural politics, and tries to construct the philosophy and structure of emancipatory literacy. His view of literacy is definded as the relation between reading the words and the world. Giroux analyzes Freire's literacy theory from two aspects, " a referent for critique " and " a narrative for agency ", and argues for positioning student voice and experience in classroom positively. Finaly, I rethink Freire's Problem Posing Education, focusing on Freire's critical literacy which is redefinded by Giroux. So I propose some prerequisites of forming critical literacy in educational practices.