Context-aware Web service is an interactive model between the context of service requesters and the services in Web-enabled environments. We envision that providing context-aware services is the first step toward ubiquitous Web services to enhance current Web-based e-business by finding right business partners, right business information, and right business services in the right place at the right time. The major contributions of this paper are the development of our context model and Context Aware Service Oriented Architecture (CA-SOA). We have developed a context model to formally describe and acquire contextual information pertaining to the service requesters and services. Based on the model, we have constructed CA-SOA for ubiquitous Web service discovery and access based on service and requesters' surrounding context.