Web Services technologies become the new and powerful tools for generation of web applications. Web Services are extremely useful when the service will be accessed by a variety of clients that are on different platform. In this thesis, a common web application -Event Ticket System is proposed with two focuses: Firstly, Web Services technologies are used to design a multi platform Event Ticketing System. The main Web Service technology adopted in this system is WSDL (Web Service Description Language). With a same web service, various client applications can be implemented to finish a whole Event Ticketing System. These client applications can be designed for mobile phone user, for normal web browser user or other types. Secondly, this system uses the XML file to represent database as the data store unit. In this way, the system maintenance is much easier. In this thesis, a prototype of the Multi-Platform Event Ticketing System with two kinds of client side applications, one is for web browser customer and the other is for mobile phone user, is implemented to prove its feasibility and efficiency. Keywords: Web Services, Electronic Ticketing System, XML