As a part of online system,user-interface takes an important role in information searching. This paper mainly discusses the following three questions about user- interface technology: (1) styles of user-interfaces, includes command language, menu selection, direct manipulation, NLP-based intelligent interface, etc; (2) user-interface systems types, such as gateway , front-ends system. inter- mediary system. Their functions are extensively explored; (3) further developments in the future, some key interface technologies are listed.