Abstract: AJAX namely asynchronous JavaScript and XML，uses JavaScript, HTML，DOM technology to design Web rich client with server background asynchronous interaction, the interaction can't interrupt the user' screen operation, it can provide better service response.月AX makes the traditional client based on Web design, and makes the same effect stand-alone GUI way of distributed system based on Web design, has produced important influence. Compared with traditional Web development way of comparison, this paper introduced core technologies and basic principle of useing AJAX Web to develope application system.

Key words: AJAX, Rich client, Web development