Abstract: The current research progresses and the existing problems of description logic(DL), especially the insufficiency of using dynamic description logic(DDL) to act as logical foundation for the semantic Web, are analyzed in this paper. According to the characteristics and requirement of the semantic Web, a kind of new description logic, i.e., distributed dynamic description logic(D3L), is presented. The syntax and semantics of D3L are given. The reasoning mechanism of D3L is mainly studied, and two kinds of reasoning methods, the direct reasoning method and the transform reasoning method, are presented. Compared with DDL, the D3L provides more reasonable logic foundation for the semantic Web, and overcomes the insufficiency of using DDL to act as logical foundation for the semantic Web.