Customer oriented Web-based modular product design system can demonstrate customer-centered design concept. The sofa design system is chosen as a sample to show how to make this be a reality. This system uses RIA as client solution which can make the user interface more lively, chooses Flexlib as component library. Spring is selected as AOP and IoC solution in the backend. Degrafa as the graphics engine, BlazeDS is chosen to make the communication between frontend and backend. So a cooperative operation environment for both customer and professional designer can be established. And the customer can self-design their style’s sofa in this environment.