The three principal indexes,including science citation index, engineering index and index to science and technology, have several kinds of media, that is, print, online, CD-ROM, and Web databases,in which the latter two are widely used. Based on collections of Tsinghua University Library, this article describes their differences in coverage, characteristics, author field., etc. Methods and techniques of searching complex author index are explored. A brief introduction to some other indexes being frequently used in scient ificevaluat ing activities has been given.