Most schools close their campus for the safety of students and teachers under COVID-19 epidemic. Online teaching is used in most schools and universities widely in spring term 2020. This paper studies on the online teaching method and results in online teaching of high frequency circuit, which is useful for online teaching of electronic engineering. In the online class, we use the discussion as the main method instead of the lecture. Students study the course contents before class. Most students are satisfied with the online teaching method. This online teaching method should be applied in other courses teaching in online university education.