The 21st century is a century that the information is popularized in full and the Internet resources are abundant, e-learning has gradually become a global phenomenon no only in formal education institutions but also in educational training organizations. Due to the rapid development of broadband Internet, online courses can now offer asynchronous learning activities as well as synchronous learning activities. Some literature have pointed out that online synchronous teaching is the key to engage online learners. How to evaluate the quality of online synchronous teaching becomes an important research topic. However, there is still very little research discussing this issue. Therefore, this study aims to develop a quality scale for evaluating online synchronous teaching from information system perspective. To achieve the research goal, we first identify some general quality indicators from literature survey; we then conduct a focus group interview to select those essential indicators. A questionnaire of the quality scale is then developed based on those essential indicators. A survey with 308 subjects has been conducted and data were collected to analyze the validity of the quality scale. The results showed that the discrimination, reliability and validity are all conformed to the standardization of scale development procedure. The result also showed that the developed quality scale has a good reliability and validity. The developed quality scale would be a good reference for administrators of educational organizations, teachers, and researchers. This quality scale will contribute to the planning and operation of the service of online synchronous teaching for administrators, and for teachers to better instructional designs for their online synchronous teaching. Researchers interested in synchronous teaching and learning can tackle the further research issues.