It becomes popular to use forum assisting teaching in the higher education. This research basing on Moore’s transactional distance theory investigates the influence of instructional design on interaction between students and teacher, content, and students. The sample is chosen from college students who study the creative problem solving course. The sample is divided into two groups: high-structured group and low-structured group. Then the research compares the transactional distance between students and instructors, contents, students and system interface. Also it compares the learning perception of students between two groups. The results shows the transactional distance between students and students can effectively predict the learning perception. Further, the learner autonomy is higher, the students feel closer.