Web service technology is a component-oriented and SOAP-based interoperable technology widely adopted in enterprise Application to Application (A2A), Business to Business (B2B), and Enterprise Application Integration (EAI) applications. Web Service component composite and connection models are the key issues to make Web service successful in the future. Web service standard and specification does not support event-based asynchronous callback which is very important for transaction or delayed business application. This paper presents a Callback Web services enable proxy approaches to implement callback in Web services without modifying existing Web services providers. In addition, a universal Callback reusable proxy design pattern is also proposed, which provides a platform, language, proprietary and technology independent service middleware for multiple clients to share and get services from multiple service providers in an asynchronous event-based implicit invocation communication mode .