In the current quality assurance mechanisms of Web services, it focuses mainly on such generic service attributes as availability, accessibility, reliability, regulatory, security, response time, throughput, latency, price, network bandwidth, reputation, etc. and ignores the important role of domain-related service attributes, related to different application domains. But domain-related attributes are essential factors in choosing and evaluating Web services for users, and domain-related quality attributes of Web services reflect the information about business contents of specific areas and service providers, which are important reference factors for customers in their evaluating the quality of a Web service and choosing it. Adopting and realizing the quality guarantee mechanism of Web services in the Web server systems, and meeting with the rising needs of Web services have already been an important content of the study of Web services. This paper, therefore, analyses domain-related service attributes, and proposes a method based on ontology and API hook for evaluating the quality of Web Services of e-commerce Websites.