1. Visual education stage: In the 1920s, as the industrial revolution promoted the rapid development of science and technology, some new scientific and technological achievements, such as photography, slide projector and silent film, were introduced into the teaching field, which brought new technical means to the traditional manual teaching. The field of educational technology then takes "media-characteristics-effect" as the research object, and the field of educational technology begins.

2. Audio-visual education stage: After the formation of systematic audio-visual education communication theory, the development of communication theory, early systematic view and learning theory introduced many new theoretical concepts to the audio-visual education field and broadened the horizons of audio-visual education theorists.

3. Audiovisual communication stage: With the continuous development of information technology, educational technology has also entered the stage of audiovisual communication. At this stage, the focus of research is to spread information by using audio-visual media, including TV, video and Internet.

4. Educational technology stage: With the continuous progress of technology, educational technology has gradually shifted from simple media and tool development to systematic teaching design. Educational technology at this stage pays more attention to students' needs and teachers' teaching methods, aiming at improving teaching quality and students' learning effect through system design and development.