Long-distance education is a very important teaching method now. The foundation of the longdistance is the construction of educational resources database. The key work of constructing resources database is to structure an appropriate index. The paper studies the representation of the characters of multimedia educational resources and the relations between the hierarchy characters. A hierarchy index is built to satisfy all kinds of queries to the educational resources database system. The subject ontology is used to get a standard annotation of the resources and a standard description of the query requirement. The subject ontology is also used to extend the semantics of the query requirement. And the mapping rules of the hierarchy characters provide a way to represent the semantics of the resource automatically.