The quality of software is very important. Comprehensive testing is considered an obvious prerequisite for high software quality, In the thesis one method is introduced to generate test cases for system functional testing from UL diagrams in a systematic way. It mainly aims at testing web application. The thesis has two parts. The first one describes how to derive test cases from UML diagrams in a systematical way, Testers can make use of Use Case diagrams, Sequence diagrams, Class diagrams, State diagrams and Activity diagrams to derive test cases, The other one explains how to store test cases using XML format. Test Case XML files can be understood easily by testers and be derived in an incremental way, They can be parsed through the existing parsers to assist the automated test case execution. A simplified E-Ticketing web application is used to illustrate the proposed method. Additionally, one testing tool is implemented, It has two functions, test case editor and test engine. By using this tool, test cases XL files can be generated and updated, and then test engine will read the files as input, run the functional testing against the web application automatically. Keywords: Functional Testing, UML, Test Case Generation, Test Case Execution, XML, Web Application