The populations of internet user gradually rise by year. It shows the competitive internet market in Taiwan. Therefore, the purpose of this study was to determine the extent of disconfirmation of the perceived quality of Portal sites services, and its relationship to service quality, customer's satisfaction and customer loyalty. In addition, the research would compare between direct measurement and gap measurement. The research result shows that service quality has positive effect on customer satisfaction and customer satisfaction has positive effect on customer loyalty. Besides, service quality measured by direct measurement is more effective than by gap measurement. The final section of this article considers the implications of this finding for Portal sites managers and future research in the area of service.