Seminar series can address cutting-edge topics not covered in existing courses, but it is time-consuming for interaction between students in large-enrolled seminars. To promote student interaction without compromising course goals, a large blended seminar series course was designed by combining traditional offline lectures and online discussions for Educational Technology Frontiers course. The study collected posts from online discussion forums. Social network analysis and descriptive statistics were used to analyze students' interaction. The study also conducted three surveys to investigate students' perceptions of course success on the aspects of subject understanding and active learning. Wilcoxon signed rank test was used to determine significant differences of students' subject understanding before and after class. Descriptive statistics were used to explore students' active learning. The results showed that the course promotes students to participate in interaction and students show a high level of enthusiasm in interaction. The study also documented a strong and positive influence on students' perceptions of their subject understanding and active learning.