Scientific texts domain keyword is one of the basic elements of the text high-level semantics acquisition, domain ontology building and the knowledge representation in semantic grid, knowledge grid and escience environment. It is also the indispensable foundation and prerequisite work of Web scientific texts automatic classification, clustering and personalized services. TFIDF based TDDF formula is proposed to extract scientific texts domain keyword. The experiments proved that TDDF formula extracting texts domain keyword is superior to the classic TFIDF formula does. Above discussions and achievements can provide certain support not only for the establishment of semantic grid, knowledge grid and escience environment, but also for the Web knowledge acquisition, representation and text information retrieval and so on.