As the way to disseminate information has been changed , we have to adjust ourselves to those newer retrieval methods aned habits, too. Hence, trying to find out efficient retrieval policies to be fast, accurate and complete while we are doing on-line searching, TULIPS, National Taiwan university OPAC System, was consulted to relate the relationship between data structure and information retrieval systems; besides, based on the characteristrics of data structure, retrieval techniques and policies are recommended. As the result shown in this study, the efficiency of on-line searching can be improved by using index, searching by subject, taking off the words frequently used.