Description Logic is now an active research area, which is applied universally to knowledge representation, Semantic Web and Ontology language. Compared with Description Logic, Distributed Description Logic can be used to better establish distributed ontologies from distributed information sources. But little attention has been paid to the problem of endowing Distributed Description Logic with default reasoning capabilities to deal with incomplete or conflict information. In this paper we present a default extension to Distributed Description Logics to handle the heterogeneity and incompleteness of different information sources. We extend Distributed Description Logics by adding default information into a distributed knowledge base, and discuss the default satisfiability based on Distributed Description Logics with default rules. To perform default reasoning, a default Tableau algorithm is developed to check satisfiability of complex concepts and subsumption assertions.