In order to understand the teaching effect of “emergency online teaching” under the background of online teaching across the whole country, , the school conducted a questionnaire survey on the effect of online teaching among all the teachers and students. The survey focused on the following aspects: overall evaluation and self-evaluation of online teaching by teachers and students; comparison between online and offline teaching strategies and learning behaviors; changes brought by online teaching among teachers and students. This study analyzes the data of the special survey and concludes that, the effect of online and offline teaching is basically equivalent though the online and offline teaching have their own advantages, and the online teaching has brought about many profound changes. In addition, the authors point out the main problems existing in the online teaching, and put forward corresponding suggestions to improve the effect of online teaching.